MODERN  DRILLING 
PRACTICE 


MODERN 
DRILLING   PRACTICE 


MODERN 
DRILLING  PRACTICE 


A  TREATISE  ON  THE  USE  OF  VARIOUS  TYPES 
OF  SINGLE-  AND  MULTIPLE  -  SPINDLE  DRILL- 
ING MACHINES,  INCLUDING  THEIR  APPLICA- 
TION TO  STANDARD  AND  SPECIAL  OPERATIONS, 
THE  RELATION  OF  SPEEDS  AND  FEEDS  TO  IN- 
TENSIVE PRODUCTION,  AND  THE  DIFFERENT 
TYPES  OF  TOOLS  AND  FIXTURES  UTILIZED  IN 
PROGRESSIVE  MACHINE  SHOPS  FOR  INCREAS- 
ING THE  RANGE  AND  EFFICIENCY  OF  MA- 
CHINES OF  THIS  CLASS 


EDWARD    K.   HAMMOND 

ASSOCIATE  EDITOR  or  MACHINERY 

JOINT  AUTHOR  OF  "  SHOP  MANAGEMENT  ANO  SYSTEMS  " 


FIRST  EDITION 


NEW  YORK 

THE    INDUSTRIAL    PRESS 

LONDON:    THE   MACHINERY   PUBLISHING   CO.,   LTD. 
1919 


y 


COPYRIGHT,  1919, 

BY 

THE  INDUSTRIAL  PRESS 
NEW  YORK 


COMPOSITION  AND  ELECTROTYPING  BY  F.  H.  GILSON  COMPANY,  BOSTON,  U.  S.  A. 


PREFACE 


DURING  recent  years,  a  number  of  important  changes  have 
been  made  in  methods  of  drilling, holes  in  the  parts  of  manufac- 
tured products.  Noteworthy  among  these  are  the  great  increase 
in  the  speed  at  which  twist  drills  are  driven,  the  application  of 
various  types  of  universal  or  special  multiple-spindle  drilling 
machines  or  auxiliary  drill  heads,  and  the  successful  employ- 
ment of  semi-automatic  drilling  machines.  All  of  these  develop- 
ments in  drilling  practice  have  been  introduced  with  the  view 
of  increasing  rates  of  production;  and,  in  preparing  the  subject 
matter  of  this  book,  the  author's  object  has  been  the  same.  The 
methods  discussed  are  those  which  have  been  thoroughly  tried 
out  under  actual  manufacturing  conditions,  so  that  their  prac- 
ticability has  been  conclusively  demonstrated.  0As  a  result, 
men  who  are  responsible  for  the  selection  of  methods  of  per- 
forming machining  operations  can  decide  upon  the  application 
of  any  of  these  suggestions  for  handling  their  own  work  with 
complete  assurance  that  the  resulting  benefits  are  likely  to  be  as 
great  as  in  the  case  of  other  plants  where  substantial  economies 
have  been  effected. 

Probably  it  is  safe  to  say  that  there  is  no  class  of  cutting  tool 
used  in  machine  shops  which  receives  as  little  consideration  as 
the  twist  drill.  This  is  largely  due  to  the  fact  that  drills  can  be 
bought  ready  for  use  in  practically  any  size.  As  a  result,  the 
mechanic  is  likely  to  assume  that  the  twist  drill  manufacturer 
has  produced  tools  which  are  not  only  ready  for  use,  but  which 
are  capable  of  remaining  in  good  condition  with  very  little 
attention.  As  a  matter  of  fact,  the  proper  grinding  of  a  twist 
drill  is  of  the  utmost  importance,  and  unless  the  drill  is  ground 
to  the  proper  shape,  its  cutting  efficiency  is  certain  to  be  very 
seriously  impaired.  Realizing  the  importance  of  proper  drill 
grinding,  a  comprehensive  discussion  has  been  presented  of  the 

.  V 

4ICG64 


VI  PREFACE 

theoretical  considerations  which  must  be  fulfilled  in  order  to 
grind  a  drill  and  maintain  th?  point  of  such  a  shape  that  it 
will  have  the  same  cutting  efficiency  as  a  new  drill  of  the  same 
size.  Drills  may  be  ground  on  either  a  special  drill  grinding 
machine  or  on  an  ordinary  tool  grinder,  and  information  is  given 
concerning  the  proper  method  of  procedure  in  both  cases. 

All  mechanics  are  familiar  with  the  various  types  of  drilling 
machines  which  are  extensively  used  in  machine  shops.  Bearing 
this  fact  in  mind,  it  was  felt  that  nothing  beyond  a  brief  descrip- 
tion of  the  essential  features  of  each  type  of  machine  would  be  of 
practical  value.  After  this  preliminary  discussion  of  machine 
design,  examples  of  good  practice  in  operating  each  type  of 
machine  are  illustrated  and  described.  In  this  connection, 
complete  information  is  given  concerning  the  material,  the  size 
of  holes  being  drilled,  the  speed  and  feed  at  which  the  operation 
is  performed,  and  the  rate  of  production  which  is  obtained. 
The  examples  selected  show  operations  which  are  conducted 
under  conditions  approximating  maximum  output  and,  as  a 
result,  should  'prove  of  value  in  suggesting  conditions  under 
which  a  new  job  may  be  successfully  handled.  No  attempt  has 
been  made  to  take  up  the  subject  of  jigs  and  fixtures  beyond 
explaining  certain  fundamental  points  in  their  design  and  the 
essential  features  of  equipments  used  in  performing  the  partic- 
ular operations  which  are  described.  The  reason  is  that  this 
subject  has  been  considered  of  sufficient  importance  to  warrant 
its  treatment  in  a  separate  volume  in  which  a  full  discussion  is 
presented  of  various  principles  of  jig  and  fixture  design. 

THE  AUTHOR 

NEW  YORK,  May,  1919. 


CONTENTS 


CHAPTER  I 

GENERAL  TYPES   OF  DRILLING   MACHINES   AND 
THEIR  APPLICATION 

PACES 

Vertical  Drilling  Machines  —  Radial  Drilling  Machines  — 
Multiple-spindle  Drilling  Machines  —  Automatic  Drilling  Ma- 
chines —  Turret-type  Drilling  Machines  —  Sensitive  Drilling 
Machines .  .  .  .. 1-27 


CHAPTER  II 

MULTIPLE-SPINDLE  DRILLING  MACHINES  OF 
STANDARD  AND   SPECIAL  DESIGN 

Multiple-spindle  Drilling  Machines  of  Straight  Line  Type 
—  Sliding  Jigs  for  Multiple-spindle  Operation  —  Use  of  Mul- 
tiple-spindle Drill  Heads  —  Machines  of  the  Cluster  Type  — 
Special  Designs  —  Drilling,  Reaming,  and  Counterboring  on 
Multiple-spindle  Machines  —  Operations  on  Machines  of  the 
Station  Type 28-62 


CHAPTER  III 

AUTOMATICALLY    CONTROLLED    DRILLING    MACHINES 
OF   SPECIAL  DESIGN 

Five-  and  Six-spindle  Semi-automatic  Machines  —  Semi- 
automatic Machines  with  Indexing  Fixture  —  Cotter-pin 
Hole  Drilling  Machine  —  Six-head  Continuous-feed  Drilling 
Machine  —  Semi-automatic  Twelve-spindle  Machine  —  Motor 
Valve  Sleeve  Multiple-drilling  Machine 63-81 


Vlll  CONTENTS 

CHAPTER  IV 
SPEEDS  AND   FEEDS  FOR  DRILLING 

PAGES 

Advantages  of  Drilling  at  High  Speed  —  Speeds  and  Feeds 

Recommended  —  Automatic     Speed     Adjustment  —  Critical 

Drilling  Speeds  —  High-speeds  of  Modern  Drilling  Machines 

-  Effect  of  High  Speeds  on  High-speed  Steel  Drills  —  Feed 

Pressure  and  Power  Required  for  Drilling 82-101 

CHAPTER  V 
TYPES  OF  DRILLS  AND  DRILL  SOCKETS 

Two-  Three-  and  Four-fluted  Twist  Drills  —  Straight-fluted 
and  Flat  Drills  —  The  Teat  Drill  —  Center  Drill  and  Coun- 
tersink—  Oil-tube  Drills  —  Hollow  and  Rifle  Barrel  Drills  — 
Spiral  and  Rake  Angles  of  Twist  Drills  —  Drill  Sockets  — 
Methods  of  Utilizing  Drills  with  Broken  Tangs 102-113 

CHAPTER  VI 
TYPES  OF  COMMONLY  USED   DRILL  CHUCKS 

Quick-change  Collet  Chucks  —  Two-jaw  Screw-type  Drill 
Chuck  — Geared    Type    of    Chuck  —  Wrenchless    Chucks  - 
Chucks  for  Special  Drill  Shanks 114-124 

CHAPTER  VII 
DRILL   GRINDING 

Requirements  in  Drill  Grinding  —  Angles  of  Drill  Points  and 
Clearance  on  the  Cutting  Edges  —  Use  of  Drill  Grinding  Ma- 
chines —  How  to  Grind  Drills  by  Hand  —  Effects  of  Improper 
Drill  Grinding  —  Causes  of  Broken  Drills  —  Strains  on  Drills 
Due  to  Feed  Pressure  —  Torsional  Resistance 125-141 


CONTENTS  ix 

CHAPTER  VIII 

DRILLING    MACHINES    APPLIED    TO    GENERAL    MANU- 
FACTURING OPERATIONS 

PAGES 

Arrangement  of  Machines  —  Number  of  Machines  used 
Progressively  —  Organization  of  Drilling  Department  —  Spe- 
cial Equipment  —  Provision  for  Threading  and  Tapping  — 
Automatic  Drilling  Mechanism  —  Disengagement  of  Feed 
for  Facing  Operations  —  Stud  Driving  ....................  142-176 


CHAPTER  IX 

JIGS,   FIXTURES,   AND   SPECIAL   TOOLS   FOR  DRILLING 

MACHINES 

Essential  Features  of  Jig  Design  —  Selection  of  Locating 
Points  —  Clamping  Devices  —  Summary  of  Important  Points 
in  Design  —  Design  of  Special  Tools  and  Fixtures  —  Accur- 
acy 'in  Tripping  of  Feed  —  Special  Features  of  Jigs  and  Fix- 
tures —  Rates  of  Production  ............................  177-201 


CHAPTER  X 
DEEP-HOLE  DRILLING 

Inverted  Drilling  for  Deep-hole  Work  —  Vertical  Deep- 
hole  Drilling  Machine  —  Horizontal  Deep-hole  Drilling  Ma- 
chine —  Drills  for  Deep  Holes  —  Rifle  Barrel  Drilling  Machine 
—  Oil  Supply  for  Rifle  Barrel  Drilling  Machine  —  Rifle  Barrel 
Reaming  Machine  ......................................  202-225 


MODERN     DRILLING     PRACTICE 


CHAPTER  I 

GENERAL   TYPES    OF   DRILLING   MACHINES 
AND   THEIR  APPLICATION 

IN  those  shops  where  the  most  remarkable  improvement  has 
been  made  in  rates  of  production  secured  on  drilling  machines, 
the  increase  has  been  largely  due  to  constantly  higher  speeds  and 
the  rates  of  feed  which  are  employed  in  the  performance  of  drill- 
ing operations,  but  more  particularly  as  a  result  of  increasing  the 
speed.  There  are  many  noteworthy  advantages  secured  through 
drilling  at  high  speed,  and  these  will  receive  detailed  considera- 
tion in  Chapter  IV  on  "  Speeds  and  Feeds  for  Drilling."  The 
remarkable  increase  in  the  speed  at  which  drilling  operations  are 
performed  has  created  a  condition  which  was  formerly  unim- 
portant, i.e.,  in  regard  to  the  relation  between  the  time  actually 
consumed  in  the  performance  of  a  drilling  operation  and  the 
time  required  for  setting  up  the  work.  Obviously,  increasing 
the  speed  and  rate  of  feed  cuts  down  the  time  required  to  drill 
a  hole,  and,  therefore,  jigs  and  work-holding  fixtures  must  be  so 
constructed  that  the  setting-up  time  does  not  become  the  lim- 
iting factor  in  performing  the  drilling  operation.  The  steps 
which  must  be  taken  to  secure  this  result  will  vary  according  to 
the  depth  of  the  hole,  and  consequently  according  to  the  time 
required  to  complete  the.  drilling  operation.  In  any  case,  the 
t,vo  chief  points  which  require  consideration  are  to  design  jigs 
and  fixtures  with  clamping  devices  which  may  be  quickly  oper- 
ated, so  that  the  minimum  amount  of  time  is  required  to  secure 
the  work  in  place  ready  to  be  drilled,  or  to  provide  jigs  or  fixtures 
of  the  so-called  indexing  type,  so  that  the  operator  may  be  set- 
ting up  a  piece  in  the  fixture  while  the  machine  is  engaged  in 
drilling  work  held  in  other  sections  of  the  fixture.  This  point 


2  MODERN  DRILLING  PRACTICE 

will  receive  detailed  consideration  in  connection  with  a  descrip- 
tion of  examples  of  drilling  machine  equipment  which  will  be 
illustrated  and  described. 

Types  of  Drilling  Machines.  —  Drilling  machines  which  find 
the  most  general  application  in  American  manufacturing  plants 
may  be  roughly  divided  into  three  general  classes,  as  follows: 

1.  Vertical  drilling  machines. 

2.  Radial  drilling  machines. 

3.  Multiple-spindle  drilling  machines. 

Each  of  these  general  classes  is  capable  of  further  subdivision, 
so  that  drilling  machines  are  finally  classified  under  the  follow- 
ing headings: 

1.  Vertical  or  "  upright  "  drilling  machines. 

2.  Vertical  sensitive  drilling  machines. 

3.  Vertical  high-duty  drilling  machines. 

4.  Radial  drilling  machines. 

5.  Multiple-spindle  drilling  machines  of  straight-line  type. 

6.  Multiple-spindle  drilling  machines  of  cluster  type. 

7.  Automatic  drilling  machines. 

8.  Turret-type  drilling  machines. 

In  addition  to  the  eight  preceding  types  of  machines,  a  great 
deal  of  useful  work  is  done  by  special  machines  built  to  meet 
the  requirements  of  individual  cases.  Such  machines  are  gen- 
erally of  the  multiple-spindle  type,  but  they  are  especially  de- 
signed for  specific  classes  of  work. 

Vertical  or  Upright  Drilling  Machines.  —  The  vertical  or  up- 
right machine  is  the  most  commonly  used  type  of  "  drill  press  " 
employed  in  the  machine  shop.  It  is  usually  equipped  with 
power  feed,  and  a  tapping  attachment  is  often  provided,  which 
may  be  engaged  to  provide  for  handling  work  in  which  holes 
have  to  be  tapped. 

The  term  "  sensitive  "  is  applied  to  those  types  of  light  drilling 
machines  which  are  equipped  with  hand  feed,  so  that  the  opera- 
tor is  able  to  judge  the  amount  of  feed  pressure  with  which  the 
drill  is  being  driven  into  the  work.  These  machines  are  usually 
adapted  for  drills  from  the  smallest  sizes  up  to  from  f  to  J  inch  in 
diameter.  They  are  used  on  a  great  variety  of  work,  and  for 


TYPES  OF  DRILLING  MACHINES  3 

handling  small  parts  in  quick-acting  jigs  or  fixtures  they  are 
capable  of  giving  very  satisfactory  results.  One  advantage  of 
the  hand  feed  is  that  an  experienced  operator  may  use  his  judg- 
ment in  releasing  the  feed  pressure,  if  he  finds  that  the  drill  has 
struck  a  hard  spot  in  the  work.  This  is  the  means  of  saving 
the  breaking  of  drills.  Machines  of  this  type  are  now  being 
built  for  operation  at  speeds  which  were  unheard  of  a  few  years 
ago.  For  instance,  some  types  of  sensitive  drilling  machines  are 
built  for  operation  at  speeds  ranging  from  10,000  to  15,000  rev- 
olutions per  minute. 

Vertical  High-duty  Drilling  Machines.  —  As  their  name  im- 
plies, high-duty  drilling  machines  are  adapted  for  the  per- 
formance of  heavy  work,  and  they  are  commonly  employed  for 
using  a  range  of  drill  sizes  running  from  the  maximum  capacity 
of  sensitive  drilling  machines  up  to  the  largest  sizes  in  which 
drills  are  made.  In  addition  to  the  performance  of  drilling 
operations,  high-duty  drilling  machines  are  used  for  a  great 
variety  of  other  classes  of  work,  including  such  operations  as 
hollow-milling,  spot-facing,  facing,  count erboring,  threading, 
tapping,  etc.  In  general,  machines  of  this  character  may  be 
employed  to  advantage  wherever  it  is  desired  to  use  a  rotating 
tool  on  stationary  work  under  conditions  where  heavy  cuts  are 
to  be  taken.  To  meet  the  requirements  of  such  severe  service, 
the  high-duty  drilling  machine  is  equipped  with  power-driven 
feed,  and  the  rates  of  feed  are  commonly  much  greater  than 
that  employed  on  sensitive  drilling  machines,  while  the  speed  at 
which  the  drill  is  operated  is  correspondingly  reduced,  owing  to 
the  greater  diameter  of  the  drill.  There  are  various  forms  of 
mechanisms  used  on  these  machines,  but  in  all  cases  provision 
is  made  for  obtaining  any  of  a  range  of  speed  and  feed  changes 
suitable  for  the  work  on  which  the  machine  is  engaged. 

Radial  Drilling  Machines.  —  On  the  familiar  type  of  radial 
drilling  machine  the  spindle  head  is  carried  on  an  arm,  which 
may  be  swung  around  the  column  of  the  machine,  and  the 
spindle  head  may  also  be  moved  back  and  forth  along  the  arm. 
This  combination  of  movements  makes  it  possible  to  locate  the 
spindle  of  a  radial  drilling  machine  at  any  desired  point  over 


4  MODERN  DRILLING  PRACTICE 

work  which  comes  within  this  range  of  movement.  Radial 
drilling  machines  are  commonly  classified  according  to  the 
length  of  arm,  i.e.,  a  6-foot  radial  drill  has  an  arm  6  feet  in 
length.  Sizes  in  which  these  machines  are  generally  built  run 
from  about  2\  to  6  feet.  Obviously,  the  size  of  the  work  which 
can  be  handled  with  a  machine  of  this  type  is  governed  by  the 
length  of  arm  and  vertical  adjustment  of  the  arm  on  the  machine 
column.  Radial  drilling  machines  are  generally  employed  for 
handling  those  classes  of  work  where  there  are  a  number  of  holes 
to  be  drilled  and  where  the  work  is  either  too  heavy  or  too  large 
to  be  conveniently  set  up  on  multiple-spindle  drilling  machines. 
Multiple-spindle  Drilling  Machines.  —  A  great  many  parts 
that  have  to  be  drilled  require  holes  of  different  diameters,  and 
other  operations,  such  as  counterboring,  reaming,  or  counter- 
sinking, are  frequently  necessary.  When  work  of  this  class  is 
done  in  a  machine  having  one  spindle,  considerable  time  is 
wasted  in  removing  one  drill  and  replacing  it  with  a  different 
size  or  with  some  other  kind  of  tool.  For  this  reason,  drilling 
machines  having  several  spindles  are  often  used  when  the  work 
requires  a  number  of  successive  operations.  The  advantage  of 
the  multiple  spindle  or  "  gang  "  type  as  applied  to  work  of  the 
class  mentioned  is  that  all  the  different  tools  necessary  can  be 
inserted  in  the  various  spindles,  and  the  drilling  is  done  by  pass- 
ing the  work  from  one  spindle  to  the  next. 

Drilling  machines  of  the  multiple-spindle  type  are  also  com- 
monly used  for  drilling  a  number  of  holes  simultaneously. 
The  arrangement  of  these  machines  is  varied  considerably  to 
suit  different  kinds  of  work,  but  they  may  be  divided  into  two 
general  classes;  namely,  those  having  spindles  which  remain  in 
the  same  plane  but  can  be  adjusted  for  varying  the  center-to- 
center  distance,  and  those  having  spindles  which  can  be  grouped 
in  a  circular,  square,  or  irregular  formation.  The  first  class 
referred  to  is  used  for  drilling  rows  of  bolt  or  rivet  holes  in  steel 
plates,  etc.,  and  the  second  type  is  adapted  to  the  drilling  of 
cylinder  flanges,  valve  flanges,  or  similar  work. 

Automatic  Drilling  Machines.  —  For  drilling  holes  in  small 
parts,  and  particularly  in  those  cases  where  the  diameter  and 


TYPES  OF  DRILLING  MACHINES  5 

depth  of  the  holes  are  not  great,  profitable  use  may  often  be 
made  of  automatic  drilling  machines.  These  are  built  in  vari- 
ous types,  which 'will  be  illustrated  and  described,  but  in  each 
case  the  aim  is  to  provide  means  of  keeping  the  drilling  spindle 
or  spindles  constantly  employed  while  the  operator  is  removing 
drilled  pieces  from  the  work-holding  fixtures  and  loading  fresh 
blanks  into  these  fixtures,  so  that  the  parts  may  be  drilled  when 
they  have  been  carried  around  under  the  drilling  spindles. 


Fig.  i.     Vertical  Drilling  Machines  equipped  with  Indexing  Fixtures 
for  Drilling  Universal  Joint  Rings 

Exceptionally  high  rates  of  production  can  be  obtained  from 
machines  of  this  type. 

Turret  Type  of  Drilling  Machines.  —  Drilling  machines  of  the 
turret  type  fill  the  same  general  place  among  drilling  machines 
that  is  taken  by  the  turret  lathe  among  machines  of  that  type. 
In  other  words,  turret  drilling  machines  are  used  in  those  cases 
where  there  is  a  sequence  of  such  operations  as  drilling,  counter- 
boring,  and  tapping  to  be  performed  on  a  piece  of  work.  Ma- 
chines of  this  type  are  equipped  with  a  turret  carried  on  a  hori- 
zontal axis  about  which  the  turret  may  be  revolved  to  bring  the 


MODERN   DRILLING   PRACTICE 


sequence  of  tools  into  the  operating  position.  In  general, 
turret-type  drilling  machines  are  used  as  an  alternate  method  of 
handling  those  classes  of  work  which  are  commonly  handled  on 
multiple-spindle  drilling  machines  of  the  straight-line  type, 
where  work  is  passed  along  from  spindle  to  spindle. 

Now  that  the  different  types  of  drilling  machines  and  classes 
of  work  for  which  each  is  adapted  have  been  considered,  a 
detailed  discussion  of  installations  of  the  different  types  of 
machines,  and  examples  of  work  for  which  each  type  is  adapted 
will  be  discussed  as  well  as  the  methods  of  setting  up  the  work 


Machinery 


Fig.  2.    Indexing  Fixture  used  on  Drilling  Machine  shown  in  Fig.  i 
for  Drilling  Four  Holes  in  Universal  Joint  Rings 

and  rates  of  production  that  are  obtained  under  favorable  con- 
ditions. The  same  order  will  be  followed  in  discussing  the  use 
of  these  machines  as  that  which  was  followed  in  mentioning  the 
different  types. 

Operation  of  Vertical  or  Upright  Drilling  Machines.  —  Fig.  i 
shows  a  group  of  three  upright  drilling  machines  built  by  the 
Rockford  Drilling  Machine  Co.,  engaged  in  drilling  universal 
joint  rings;  and  a  fourth  machine  to  the  left  is  employed  for 
reaming  the  holes.  The  three  drilling  machines  are  equipped 
with  indexing  jigs  to  provide  for  bringing  the  work  into  the 
required  positions  for  successively  drilling  each  of  the  four  holes. 
A  detailed  view  of  the  indexing  jig  is  shown  in  Fig.  2.  Referring 


TYPES  OF  DRILLING  MACHINES 


to  this  illustration,  it  will  be  seen  that  work  A  is  clamped  in 
place  under  bushing  B  and  that  provision  for  locating  the  work 
in  the  four  drilling  positions  is  made  by  means  of  index  plate  C 
and  spring  plunger  D.  The  work  to  be  drilled  is  a  drop-forging 
containing  from  0.15  to 
0.25  per  cent  of  carbon, 
from  0.30  to  0.60  per 
cent  of  manganese,  sul- 
phur below  0.045  Per 
cent,  and  phosphorus 
below  0.05  per  cent. 
The  holes  to  be  drilled 
are  i  inch  in  diameter 
by  T9F  inch  in  depth. 
The  production  is  ap- 
proximately 600  com- 
pleted rings  on  the 
three  right-hand  drill- 
ing machines  in  a  ten- 
hour  working  day,  i.e., 
2400  holes  are  drilled 
per  day  in  these  forg- 
ings. 

High-speed  Ball- 
bearing  Sensitive  Drill- 
ing  Machines.  —  To 
take  advantage  of  the 
benefits  which  are  se- 
cured through  the  per- 
formance of  drilling  op- 


Fig.  3.    Sensitive  Drilling  Machine  with  Special 
Jig  for  Drilling  Cross-holes  in  Pins 


erations  at  high  speed, 
the  Leland-Gifford  Co.  builds  a  line  of  ball-bearing  sensitive  drill- 
ing machines  which  are  adapted  for  operation  at  speeds  ranging 
from  10,000  to  15,000  revolutions  per  minute.  These  ma- 
chines are  built  in  a  bench  type  or  with  a  pedestal  base 
so  that  they  may  be  set  up  on  the  floor.  Fig.  3  shows  one 
of  the  pedestal  type  machines  equipped  with  a  special  drill- 


8 


MODERN  DRILLING  PRACTICE 


ing  jig  built  by  Caulkins  &  Carpenter,  and  a  better  idea  of 
the  way  in  which  this  outfit  operates  will  be  gathered  from 
Fig.  4.  This  jig  is  especially  suited  for  use  in  drilling  cross- 


Fig.  4.     Quick-acting  Jig  for  Drilling  Cross-holes  in  Pins 

holes  in  pins  and  similar  shaped  parts,  and,  to  meet  the  re- 
quirements of  such  work,  it  is  furnished  with  a  V-block  A  to 
hold  the  work  and  an  end-stop  B  to  locate  the  work  in  the  de- 
sired position  in  the  jig.  End-stop  B  is  connected  to  a  piston 
in  air  cylinder  C,  and  this  cylinder  is  connected  by  a  rubber  hose 
with  cylinder  D.  A  rack,  which  meshes  with  the  feed  pinion  on 


TYPES  OF  DRILLING  MACHINES  9 

the  machine,  is  carried  at  the  upper  end  of  a  rod  connected  with 
the  piston  in  cylinder  D,  and  it  will  be  apparent  that,  during  the 
time  the  drill  is  being  fed  into  the  work,  the  rack  carried  at  the 
back  of  the  feed  pinion  is  raised,  thus  raising  the  piston  in 
cylinder  D. 

After  the  drilling  operation  has  been  completed  and  the  drill 
spindle  starts  to  rise,  the  reverse  movement  of  the  feed  pinion 
drives  down  the  piston  in  cylinder  Z>,  and  this  results  in  driving 
air  through  the  flexible  tube  into  cylinder  C.  The  result  is  that 
end-stop  B  is  driven  forward  and  ejects  the  drilled  piece  from  the 
V-block.  During  this  time  the  operator  has  picked  up  another 
piece  of  work  which  he  can  immediately  place  in  position  ready 
to  be  drilled,  so  that  the  operation  of  the  machine  may  be  prac- 
tically continuous.  When  the  work  has  been  placed  in  the 
V-block  and  the  drill  starts  to  feed  down,  raising  of  the  piston 
in  cylinder  D  results  in  actuating  a  link  mechanism  at  the  back 
of  the  jig,  which  is  responsible  for  clamping  the  work  in  place. 

As  shown  in  the  illustration,  the  V-block  which  supports  the 
work  is  carried  on  a  knee  which  may  be  adjusted  vertically  to 
provide  for  holding  pieces  of  various  diameters;  the  rod  which 
carries  end-stop  B  and  cylinder  C  may  also  be  adjusted  in  its 
bearing  in  the  knee  to  provide  for  drilling  pins  of  different 
lengths,  and  it  is  obviously  an  easy  matter  to  substitute  drill 
bushings  of  the  correct  size  for  handling  different  operations. 
In  drilling  holes  through  pins  made  of  screw  stock  ^\  inch  in 
diameter  with  a  No.  51  drill,  the  machine  was  operated  at  6700 
revolutions  per  minute  and  produced  2200  pieces  an  hour.  Such 
a  high  rate  of  production  would  not  be  possible  were  it  not 
for  the  provision  made  in  designing  this  jig  for  rapid  handling. 

Semi-automatic  Sensitive  Drilling  Machine.  —  Fig.  5  shows 
a  high-speed,  ball-bearing  sensitive  drilling  machine  built  by 
the  Leland-Gifford  Co.  The  spindles  are  mounted  in  ball  bear- 
ings, so  that  the  machine  is  adapted  for  running  at  speeds  up  to 
3500  revolutions  per  minute.  It  is  known  as  a  "  semi-auto- 
matic "  machine,  and  in  this  respect  deviates  from  what  is  gen- 
erally understood  to  constitute  a  sensitive  drilling  machine,  be- 
cause the  spindles  are  equipped  with  power  feed.  In  operating 


10  MODERN  DRILLING  PRACTICE 

the  machine,  one  man  attends  J:o  both  spindles ;  he  sets  a  piece  of 
work  up  in  one  fixture  and  engages  the  power  feed,  then  reaches 
over  to  the  second  fixture,  removes  the  drilled  piece  of  work,  sets 
up  a  fresh  piece  in  the  fixture,  and  engages  the  power  feed.  By 
this  time  the  drilling  operation  on  the  piece  under  the  first 


Fig.  5.    Sensitive  Drilling  Machine  equipped  with  Power  Feed  which 
enables  One  Operator  to  keep  Two  Spindles  Constantly  in  Operation 

spindle  has  been  completed,  at  which  time  the  feed  is  automati- 
cally tripped  and  the  spindle  returned  to  the  starting  point,  so 
that  the  operator  merely  has  to  remove  the  drilled  piece  and 
substitute  a  fresh  blank.  In  this  way,  both  spindles  of  the 
drilling  machine  and  the  man  employed  to  operate  them  are 


TYPES  OF  DRILLING  MACHINES  11 

kept  busy  almost  all  of  the  time,  so  that  an  unusually  high 
rate  of  efficiency  is  secured.  The  lever  which  engages  the 
power  feed-clutch  may  also  be  used  to  feed  the  drill  by  hand; 
and  by  simply  pushing  up  this  lever,  the  power  feed  may  be 
instantly  disengaged  in  any  position,  without  waiting  for  the 
full  downward  movement  to  be  completed.  This  last-named 
feature  is  often  of  great  convenience. 

Particular  attention  is  called  to  the  design  of  the  jigs  used 
on  this  machine.  In  the  case  of  the  f-inch  set-collar  shown 
under  the  left-hand  spindle,  the  operation  consists  of  drilling 
a  |-inch  tap-hole  which  is  f  inch  deep  in  a  malleable-iron 
part.  The  work  is  slipped  over  pilot  A  and  secured  by  a  bell- 
mouthed  bushing  operated  by  lever  B.  In  the  case  of  the 
malleable-iron  cranks  which  are  being  drilled  under  the  right- 
hand  spindle,  a  bell-mouthed  bushing  is  also  employed  to 
secure  the  work,  this  bushing  being  operated  by  lever  C.  In 
this  case,  a  stronger  spring  is  required  to  hold  the  work; 
therefore,  a  longer  lever  is  necessary.  The  hole  being  drilled 
in  these  cranks  is  f  inch  in  diameter  by  £  inch  deep.  It 
will  be  apparent  that  in  both  cases  work  may  be  set  up  and 
removed  with  a  minimum  expenditure  of  time,  which  is  im- 
portant, because  the  operations  are  soon  finished.  In  drilling 
the  set-collars,  the  operation  is  performed  at  noo  revolu- 
tions per  minute  with  a  feed  of  0.005  inch  per  revolution, 
and  the  production  is  4800  pieces  per  eight-hour  day.  In 
drilling  the  small  cranks,  the  drill  runs  at  the  same  speed  and 
feed  and  2400  pieces  are  produced  in  eight  hours.  The  power 
feed  used  in  this  machine  is  so  designed  that,  when  the  operator 
grasps  either  of  the  feed-levers  D  and  pulls  it  forward,  feed  is 
engaged  and  the  drill  is  advanced  into  the  work  by  power  until 
an  automatic  trip  throws  out  the  feed-clutch,  at  which  time  the 
spindle  is  automatically  returned  to  the  starting  position.  Grad- 
uated circles  which  are  furnished  on  each  of  these  feed-clutches 
provide  for  setting  the  feed  to  be  tripped  after  a  hole  has  been 
drilled  to  a  predetermined  depth. 

Sensitive  Machine  arranged  to  Automatically  Control  Spin- 
dle Movements.  —  Fig.  6  shows  a  No.  2\  high-duty,  ball-bear- 


12 


MODERN  DRILLING  PRACTICE 


ing  sensitive  drilling  machine  built  by  the  Cincinnati  Pulley 
Machinery  Co.  This  machine  is  illustrated  in  use  drilling  steel 
bushings  where  it  is  required  to  drill  a  ^|-inch  hole  through  a 
wall  g-92  inch  in  thickness.  These  pieces  are  turned  out  by  an 
unskilled  operator  at  the  rate  of  1186  pieces  per  hour,  or  approxi- 
mately 10,000  pieces  in  a  ten-hour  day.  The  daily  figure  allows 
time  for  changing  drills  and  for  further  unavoidable  losses. 
Machines  of  this  type  are  built  with  either  plain  hand  feed  or 
with  power  feed,  and  means  are  provided  for  automatically 


Fig.  6.  Ball-bearing  Sensitive  Drilling  Machine  set  up  for  Use 
in  Drilling  Steel  Bushings.  On  this  Operation  the  Production 
is  10,000  Bushings  in  a  Ten-hour  Day 

reversing  the  travel  of  the  spindle  in  one  or  both  directions. 
The  machine  equipped  with  automatic  feed  mechanism  is  quite 
flexible,  it  being  possible  to  operate  it  as  a  fully  automatic  or 
semi-automatic  machine,  or  the  automatic  mechanism  may  be 
entirely  disconnected  and  the  machine  fed  by  hand.  In  shops 
which  have  pieces  that  are  manufactured  in  large  quantities, 
and  where  the  nature  of  the  work  is  such  that  it  may  be  rapidly 
set  up  and  removed  from  fixtures,  the  fully  automatic  mechanism 
is  usually  employed.  On  the  other  hand,  where  the  work  is 
comparatively  difficult  to  handle,  more  time  will  be  required 


TYPES  OF  DRILLING  MACHINES  13 

between  successive  strokes  of  the  drill,  and  for  such  work  the 
automatic  trip  for  the  down-feed  of  the  drill  is  thrown  out.  In 
this  case,  the  return  of  the  spindle  is  automatic,  but  the  power 
feed-clutch  must  be  engaged  by  hand.  For  still  other  classes 
of  work,  all  of  the  automatic  movements  are  disconnected.  The 


Fig.  7.    High-duty  Drilling  Machine  equipped  with  Indexing  Fixture 
and  Special  Three-spindle  Head  for  Drilling,  Reaming,  and  Facing 

trips  for  the  automatic  movements  may  be  set  so  that  the  time 
between  strokes  is  just  enough  to  allow  the  operator  to  remove 
the  drilled  piece  and  substitute  a  fresh  casting. 

Vertical  High-duty  Drilling  Machines.  —  For  drilling,  ream- 
ing, and  facing  the  o.ggS-inch  hole  in  rear  spring  center  brackets 


14  MODERN  DRILLING  PRACTICE 

used  in  the  construction  of  automobiles  of  its  manufacture, 
the  Willys-Overland  Co.  employs  high-duty  drilling  machines 
built  by  Baker  Bros.,  one  of  these  machines  being  shown  in 
operation  in  Fig.  7.  The  nature  of  the  work  is  such  that  a  con- 
siderable amount  of  time  must  necessarily  be  employed  in  setting 
up  the  work  in  the  fixture,  but,  as  the  depth  of  the  hole  to  be 
drilled,  reamed,  and  faced  is  also  considerable,  this  need  not 
constitute  an  unsurmountable  barrier  against  the  attainment  of 
efficient  production.  The  problem  has  been  adequately  solved 
through  adoption  of  the  use  of  an  indexing  work-holding  fixture. 
The  pieces  have  to  be  drilled,  reamed,  and  faced,  and  these 
operations  are  performed  by  tools  shown  at  A,  B,  and  C,  respec- 
tively. The  drilling  operation  naturally  consumes  the  greatest 
amount  of  time,  and  while  the  drill  is  in  operation  the  workman 
has  ample  time  to  remove  one  drilled  piece  from  the  loading 
station  at  the  front  of  the  fixture  and  substitute  a  fresh  blank; 
then,  when  the  machine  spindle  lifts  the  multiple  head  which 
drives  the  three  tools,  the  operator  pushes  the  fixture  around 
until  the  index-pin  locates  it  at  the  next  station.  For  each 
traverse  of  the  drilling  machine  spindle,  it  will  be  apparent  that 
one  finished  piece  is  produced,  as  the  drilling,  reaming,  and 
spot-facing  operations  are  performed  simultaneously. 

The  work  is  malleable  iron,  and  referring  to  the  piece  shown 
leaning  against  the  fixture  at  the  front,  attention  is  called  to  the 
fact  that  two  locating  pins  enter  holes  D  and  E,  which  were 
drilled  in  a  previous  operation.  Swinging  clamp  F  is  then 
brought  up  against  the  front  of  the  work  and  secured  by  nut  G 
that  is  tightened  with  a  wrench.  The  hole  //  to  be  drilled  is 
0.998  inch  in  diameter  by  3^  inches  deep,  and  the  rate  of  pro- 
duction is  600  pieces  per  eight-hour  day.  The  operation  is  per- 
formed at  a  speed  of  300  revolutions  per  minute  with  a  feed  of 
0.024  mcn  per  revolution.  The  machine  is  equipped  with  a  three- 
spindle  auxiliary  head  built  in  the  Willys-Overland  factory; 
pilots  J  and  K,  which  extend  up  from  the  work-holding  fixture 
into  bushings  in  the  drill  head,  assure  permanent  alignment. 

Special  Work  on  High-duty  Machine.  —  In  connection  with 
the  general  discussion  of  high-duty  drilling  machines,  mention 


TYPES  OF  DRILLING  MACHINES  15 

was  made  of  the  fact  that  machines  of  this  type  are  well  adapted 
for  the  performance  of  many  other  operations  besides  drilling. 
In  Fig.  8,  one  of  the  Baker  high-duty  drilling  machines  is  shown 
set  up  to  provide  for  simultaneously  spot-facing  three  pads  on  a 


Fig.  8.  High-duty  Drilling  Machine  equipped  with  a  Two-station 
Work-holding  Fixture  and  Special  Three-spindle  Head  for  Spot- 
facing 

universal  joint  spider.  The  machine  used  for  this  purpose  is 
equipped  with  a  three-spindle  multiple  head,  and  this  head  is 
piloted  from  the  fixture,  as  in  the  preceding  case.  The  pads 
on  these  spiders  have  to  be  spot-faced  on  both  sides,  and  to 


16  MODERN  DRILLING  PRACTICE 

provide  for  turning  over  the  work  or  for  removing  a  finished 
piece  from  the  fixture  and  substituting  a  fresh  malleable-iron 
casting,  so  that  any  idle  time  of  the  machine  may  be  reduced  as 
far  as  possible,  use  is  made  of  a  sliding  fixture  of  the  type  shown. 


Fig.  9.  High-duty  Drilling  Machine  equipped  with  Indexing  Fix- 
ture and  Two-spindle  Head  for  Hollow-milling  Steering-gear 
Housings 

This  fixture  is  furnished  with  two  stops,  one  of  which  is  shown 
at  A,  which  limit  the  travel  of  the  fixture  in  either  direction  to 
provide  for  locating  the  work  supported  at  one  or  the  other  of 
the  two  stations  on  the  fixture  under  the  spot-facing  tools.  The 


TYPES  OF  DRILLING  MACHINES  17 

holes  in  these  spiders  have  already  been  drilled,  and  these  are 
employed  as  locating  points;  in  addition,  the  pins  B  which 
locate  the  work  from  these  holes  extend  up  sufficiently  through 
the  work  so  that  the  spot-facing  tools  may  be  piloted  over 
them  to  assure  rigidity.  Owing  to  the  ingenious  way  in  which  the 
design  of  this  fixture  has  been  worked  out  and  applied,  these 
malleable-iron  spiders  may  have  three  pads  spot-faced  on  both 
sides  with  a  production  of  288  parts  per  eight-hour  day  from 
each  machine.  The  machine  is  run  at  200  revolutions  per 
minute  with  hand  feed. 

Another  example  which  tends  tq>show  the  range  of  work 
that  may  be  efficiently  handled  on  high-duty  drilling  machines 
is  illustrated  in  Fig.  9,  which  shows  the  operation  of  hollow- 
milling  steering-gear  housings  for  the  Willys-Overland  car. 
Here,  again,  use  is  made  of  an  indexing  work-holding  fixture, 
and  the  machine  is  equipped  with  a  special  two-spindle  auxiliary 
head.  To  provide  the  degree  of  rigidity  that  is  required  under 
severe  service  of  this  kind,  however,  the  system  of  piloting  is 
somewhat  different  from  that  shown  on  preceding  machines  of 
this  type.  In  this  case,  two  pilots  are  employed;  the  central 
pilot  A  is  carried  by  the  fixture  and  runs  in  a  bushing  in  the 
drill  head,  while  pilot  B  is  carried  by  the  head  and  runs  in  sockets 
carried  by  the  fixture.  This  fixture  is  indexed  through  180 
degrees,  and  in  this  position  pilot  B  will  run  in  socket  C. 

In  performing  this  hollow-milling  operation,  the  two  pieces  of 
work,  D  and  £,  are  dropped  over  pilots  on  the  fixture,  and  the 
ends  of  these  pieces  simply  bear  against  lugs  on  the  fixture  which 
prevent  them  from  turning.  Where  this  method  of  securing 
work  can  be  employed,  it  is  extremely  satisfactory,  because  the 
length  of  time  required  to  set  up  the  work  in  place  for  machining 
is  reduced  very  close  to  a  minimum.  The  holes  have  been 
machined  by  a  previous  operation  and  are  employed  as  the 
locating  points.  After  setting  up  the  work  the  fixture  is  indexed 
through  1 80  degrees,  as  previously  mentioned,  and  this  brings 
the  blanks  into  the  position  shown  in  the  illustration  where  two 
pieces  may  be  milled  simultaneously.  The  hollow-milling  cut- 
ters used  on  this  machine  are  provided  with  pilots  which  enter 


1 8  MODERN  DRILLING  PRACTICE 

bushings  F  and  G  in  the  studs  on  which  the  work  is  carried,  so 
that  further  provision  is  made  to  guard  against  vibration.  The 
length  of  time  consumed  by  this  hollow-milling  operation  is 
ample  to  allow  the  finished  pieces  to  be  removed  from  the  fixture 
and  new  blanks  to  be  set  up.  The  material  is  malleable  iron; 
and  the  surface  finished  during  this  operation  is  3^  inches  in 
length  by  i\  inches  in  diameter;  the  rate  of  production  is  160 
pieces  per  eight-hour  working  day.  This  operation  is  performed 
at  70  revolutions  per  minute  with  a  feed  of  o.oio  inch  per  revo- 
lution. 

By  employing  a  carefully  worked  out  design  for  tools  and 
work-holding  fixtures,  there  are  many  classes  of  work  on  which 
a  considerable  sequence  of  operations  may  be  performed  through 
the  use  of  high-duty  drilling  machines,  one  of  which  is  shown  in 
Fig.  10  which  illustrates  one  of  the  Baker  high-duty  drilling 
machines  equipped  with  tools  and  an  indexing  fixture  to  provide 
for  boring  and  reaming  holes  of  three  diameters  in  the  Willys- 
Overland  steering-gear  housing,  facing  the  surface  at  the  top  of 
this  housing,  facing  off  a  seat  for  the  ball  bearing,  and  tapping 
one  of  the  bored  holes.  As  in  the  preceding  case,  a  double 
system  of  pilots  is  employed,  one  of  which  is  secured  to  the  work- 
holding  fixture  and  enters  a  bushing  in  the  three-spindle  auxiliary 
head  provided  on  the  machine,  while  the  other  pilot  is  carried  by 
this  special  auxiliary  head  and  runs  in  a  sequence  of  bushings 
provided  for  that  purpose  in  the  work-holding  fixture.  Rough- 
boring  of  the  holes  of  different  diameters  is  performed  by  bits 
carried  in  bar  A.  Then,  when  the  work  is  indexed  to  the  next 
position,  the  combination  reaming  and  facing  tool  B  reams 
the  three  bored  holes  and  faces  both  the  top  of  the  steering- 
gear  housing  and  the  ball  bearing  seat.  After  this  has  been 
accomplished,  the  work  is  indexed  once  more  and  the  tap  C 
cuts  the  thread  in  the  large  hole.  To  provide  for  this  last 
operation,  the  tapping  spindle  is  furnished  with  a  hand-feed 
lever  D,  and  after  the  tap  has  penetrated  to  the  desired  depth, 
it  is  reversed  and  backed  out  of  the  hole.  This  reversal  of 
motion  is  through  gearing  operated  by  lever  E. 

In  this  connection,  attention  is  called  to  the  fact  that  all  the 


TYPES  OF  DRILLING  MACHINES 


auxiliary  heads  employed  on  these  heavy-duty  Baker  Bros, 
drilling  machines  are  counterweighted,  the  arrangement  being 
clearly  indicated  at  the  right-hand  side  of  the  machine  shown  in 


Fig.  10.  High-duty  Drilling  Machine  with  Indexing  Fixture  and 
Three-spindle  Head  for  Boring  and  Reaming  Three  Holes, 
Facing  Two  Surfaces,  and  Tapping  One  Hole 


Fig.  10.  The  fixture  used  to  support  the  work  for  performing 
the  preceding  operations  is  interesting.  The  work  is  placed 
over  a  pilot  that  enters  a  hole  bored  by  a  preceding  operation, 


20  MODERN  DRILLING  PRACTICE 

and  is  then  clamped  at  either  end  by  jaws  actuated  by  a  screw 
threaded  right-  and  left-hand  at  opposite  ends,  which  is  turned 
by  crank  F.  The  work  is  further  secured  in  place  by  clamp  Gy 
and  in  this  connection  attention  is  called  to  the  second  clamp  H, 
which  is  not  in  use.  The  reason  for  this  is  interesting,  as  it 
shows  an  economy  effected  in  the  design  of  work-holding  fixtures. 
Cars  built  for  American  use  are  generally  equipped  with  the 
steering-wheel  at  the  left,  while  those  exported  to  Europe  have 
the  steering-wheel  at  the  right.  This  makes  it  necessary  to 
machine  steering-gear  housings  for  both  types  of  design,  but  to 
avoid  the  necessity  of  an  additional  investment  in  jig  and  fixture 
equipment,  or  the  loss  of  time  and  incidental  expense  which 
would  be  involved  in  changing  from  one  type  of  work-holding 
fixture  to  another,  the  fixture  shown  in  Fig.  10  is  made  "  uni- 
versal," in  that  it  will  hold  either  type  of  steering-gear  housings. 
The  only  change  is  that,  for  holding  a  housing  of  the  opposite 
hand,  the  piece  will  rest  in  the  fixture  in  the  opposite  direction, 
and  in  that  case  clamp  //  will  be  employed  and  clamp  G  will 
remain  idle.  The  holes  bored  and  reamed  during  this  series 
of  operations  are  2§  by  -jf ,  2^  by  y|,  and  i^  by  if  inch  in 
diameter  and  depth,  respectively;  the  first  of  these  three  holes 
is  the  one  to  be  tapped.  These  pieces  are  made  of  malleable 
iron  and  the  rate  of  production  is  120  pieces  per  eight-hour  day. 

Radial  Drilling  Machines.  —  Where  there  are  a  number  of 
holes  to  be  drilled  over  the  area  of  a  piece  of  work  that  is  too 
large  or  too  heavy  to  enable  all  of  the  holes  to  be  conveniently 
reached  by  a  multiple-spindle  drilling  machine,  use  is  generally 
made  of  a  radial  drilling  machine  on  which  the  combined  move- 
ment secured  by  swinging  the  radial  arm  and  adjusting  the 
position  of  the  drill  spindle  head  on  this  arm  will  enable  all  of 
the  holes  to  be  reached  with  a  single  setting  of  the  work.  Radial 
drilling  machines  are  also  employed  in  some  cases  where  the  size 
of  the  holes  to  be  drilled  and  the  material  is  such  that  the  ser- 
vice would  be  too  severe  for  many  classes  of  multiple-spindle 
machines. 

Fig.  ii  shows  a  typical  example  of  radial  drilling  machine 
work,  which  consists  of  drilling  holes  in  the  air-head  of  a  blow- 


TYPES  OF  DRILLING  MACHINES 


21 


ing  engine.  The  view  shown  is  in  the  shops  of  the  Mesta  Ma- 
chine Co.,  and  the  radial  drilling  machine  is  a  product  of  the 
American  Tool  Works  Co.  In  the  Mesta  Machine  Co.'s  shops, 


Fig.  ii. 


Radial  Drilling  Machine  engaged  in  machining  Air- 
head of  Blowing  Engine 


radial  drilling  machines  are  also  used  to  a  considerable  extent  for 
the  performance  of  machining  operations  on  castings  of  such 
size  and  weight  that  they  sometimes  exceed  the  maximum  capa- 
city of  the  7 5 -ton  electric  cranes  in  the  shop,  and  in  any  case 


22 


MODERN  DRILLING  PRACTICE 


would  be  far  too  heavy  to  enable  them  to  be  set  up  on  any  drill- 
ing machine.  For  this  class  of  work  the  radial  drills  are  furn- 
ished with  eyes  so  that  they  can  be  picked  up  by  the  crane  hook 
and  carried  to  the  work  instead  of  following  the  general  practice 
of  taking  work  to  the  machine.  For  handling  these  exception- 
ally large  pieces  which  are  constantly  going  through  the  Mesta 
shops,  the  use  of  portable  machines  is  practically  a  matter  of 


Fig.  12. 


Radial  Drilling  Machine  engaged  in  drilling  Bed  of  a 
Machine  Tool 


necessity;  at  the  same  time,  their  application  has  been  found 
beneficial  in  that  it  is  possible  to  have  a  number  of  machines 
working  simultaneously  on  one  of  these  large  castings,  so  that 
the  time  required  to  complete  the  various  machining  opera- 
tions is  substantially  reduced. 

Fig.  1 2  shows  a  radial  drilling  machine  built  by  the  Cincinnati 
Bickford  Tool  Co.  This  machine  is  shown  engaged  on  a  typical 
radial  drilling  operation;  namely,  drilling  all  of  the  holes  in  a 


TYPES  OF  DRILLING  MACHINES 


machine  bed  casting.  This  machine  is  used  in  the  plant  of  the 
Cleveland  Automatic  Machine  Co.,  where  it  is  engaged  in  drill- 
ing fifty-two  holes  in  the  bed  of  a  Cleveland  automatic.  '  The 
operations  comprise  drilling,  reaming,  counterboring,  and  tap- 


Fig.  13.     Turret  Type  of  Drilling  Machine  in  which  Turret 
revolves  in  Vertical  Plane 

ping  holes  varying  from  i\  down  to  \  inch  in  diameter;  the 
largest  counterbore  is  4  inches  in  diameter.  The  spindle  of  the 
machine  is  equipped  with  a  quick-change  chuck,  and,  located 
conveniently  for  the  operator,  there  will  be  seen  a  portable 


24  MODERN  DRILLING  PRACTICE 

stand  on  which  are  carried  the  different  drills,  counterbores, 
reamers,  etc.,  which  are  required  in  carrying  out  the  work. 

Turret-type   Drilling   Machines.  —  Turret-type   drilling  ma- 
chines fill  the  same  place  in  the  drilling  machine  group  that  is 


Fig.  14.     Turret  Type  of  Drilling  Machine  in  which  Turret 
revolves  in  Horizontal  Plane 

occupied  by  turret  lathes  in  the  lathe  group.  From  this,  it  will 
be  obvious  that  turret  drilling  machines  are  employed  for  the 
performance  of  a  sequence  of  operations  on  a  piece  of  work 


TYPES  OF  DRILLING  MACHINES  25 

without  requiring  the  setting  of  the  work  to  be  changed.  Fig.  13 
shows  a  machine,  built  by  A.  E.  Quint,  in  which  the  required 
series  of  drills,  counterbores,  taps,  etc.,  are  mounted  in  spindles 
carried  by  a  turret  which  can  be  revolved  to  bring  the  required 
spindles  into  successive  operation.  On  this  machine,  the  de- 
sign has  been  so  worked  out  that  the  only  spindle  which  re- 
volves is  the  one  carrying  the  tool  that  is  in  the  operating 
position.  One  of  the  chief  claims  made  for  this  type  of  ma- 
chine is  that  time  is  saved  through  avoiding  the  necessity  of 
resetting  the  work  for  performing  a  sequence  of  operations, 
and  by  having  the  entire  equipment  for  performing  these  opera- 
tions contained  in  a  single  unit  an  economy  is  effected  in  both 
floor  space  and  the  required  investment  in  machine  tool  equip- 
ment. Fig.  13  shows  one  of  these  machines  in  operation,  and 
attention  is  called  to  the  fact  that  different  types  and  sizes  of 
machines  are  provided  for  the  performance  of  various  classes  of 
work. 

In  the  turret-type  drilling  machines  built  by  the  Turner 
Machine  Co.,  a  different  principle  is  employed  for  bringing  the 
required  sequence  of  tools  into  operation.  Fig.  14  shows  one  of 
these  machines  in  operation  at  the  plant  of  the  Greenfield  Tap 
&  Die  Corporation,  where  it  is  engaged  in  the  performance  of  a 
series  of  operations  on  threading  dies.  This  machine  is  shown 
drilling  one  hole  to  two  different  diameters,  and  it  is  necessary 
to  ream  one  section  of  the  hole.  The  method  of  bringing  the 
different  tools  into  operation  is  different  from  that  of  the  ma- 
chine shown  in  the  preceding  illustration.  Here  the  turret  is 
carried  on  a  vertical  spindle,  about  which  it  revolves  horizon- 
tally to  index  the  different  spindles  into  the  working  position. 
Only  the  spindle  in  the  operating  position  revolves.  Machines 
of  this  type  are  built  in  different  sizes,  so  that  a  suitable  size 
may  be  selected  for  handling  work  covering  a  considerable 
range.  These  machines  are  designed  with  a  turret  case  that 
holds  the  turret  rigidly  against  side  play,  and  a  detent  and 
socket  positively  lock  the  turret  against  rotary  movement. 
Different  styles  in  which  these  machines  are  built  provide  for 
driving  tools  fitted  with  Nos.  2,  3,  and  4  Morse  taper  shanks, 


26 


MODERN  DRILLING  PRACTICE 


so  that  machines  of  this  type  may  be  used  for  the  performance  of 
machining  operations  in  a  wide  range  of  work. 

Another  equipment  of  somewhat  the  same  general  type  is 
built  by  the  Newman  Mfg.  Co.;  the  difference  between  this 
equipment  and  the  two  preceding  types  is  that,  in  the  present 


Fig.  15.    Auxiliary  Turret  Head  to  adapt  Single-spindle  Drilling 
Machine  for  Rapid  Performance  of  a  Sequence  of  Operations 

case,  a  turret  head  is  provided  for  use  on  a  single-spindle  drill- 
ing machine.  Fig.  15  shows  a  machine  equipped  in  this  way, 
from  which  it  will  be  seen  that  the  turret  head  is  furnished 
with  spindles  for  carrying  the  required  sequence  of  tools.  The 
drive  is  so  designed  that  the  only  tool  which  rotates  is  the  one  in 


TYPES  OF  DRILLING  MACHINES  27 

the  operating  position.  The  different  spindles  are  held  in  place 
by  a  locking  mechanism  and  may  be  quickly  changed  to  bring 
successive  tools  into  the  operating  position.  A  sleeve  on  the 
head  is  attached  to  the  quill  surrounding  the  drilling  machine 
spindle,  and  provides  for  locking  the  head  at  the  proper  height. 
These  drilling  machine  turret  heads  are  made  in  two  sizes  for 
No  2  and  No.  4  Morse  taper  shanks;  they  are  also  made  to 
hold  straight  shanks,  if  so  desired. 


CHAPTER  II 

MULTIPLE-SPINDLE  DRILLING   MACHINES  OF   STANDARD 
AND   SPECIAL   DESIGN 

THE  vertical  drilling  machine  is  commonly  built  with  from 
one  to  six  spindles,  and  the  terms  "  multiple  spindle  "  and 
"  gang "  are  used  somewhat  indiscriminately  in  referring  to 
machines  of  this  type.  Probably  the  best  opinion  favors  the 
use  of  the  term  "  gang"  in  cases  where  separate  drilling  machine 
units  with  individual  drive  are  bolted  to  a  common  bed  casting, 
while  the  term  "  multiple  spindle  "  is  understood  to  designate 
machines  of  this  type  on  which  all  of  the  spindles  are  carried  in 
a  machine  frame  of  unit  construction  and  are  driven  by  a  com- 
mon driving  shaft.  In  any  case,  the  use  made  of  both  gang 
and  multiple-spindle  machines  covers  two  general  classes  of 
work.  In  one  of  these  the  machine  is  employed  for  the  per- 
formance of  a  sequence  of  operations  on  a  piece  of  work  which  is 
passed  along  from  spindle  to  spindle.  On  work  of  this  type  one 
or  more  operators  are  employed,  according  to  the  length  of 
time  required  to  perform  the  various  drilling,  counterboring, 
and  tapping  operations.  The  other  general  class  of  work  handled 
on  straight-line  multiple-spindle  or  gang  drilling  machines  is 
where  it  is  required  to  drill  a  number  of  holes  in  a  piece,  a  case 
in  point  being  where  a  line  of  holes  is  to  be  drilled  in  a  pipe. 
For  operations  of  this  kind  the  machines  are  so  equipped  that 
all  of  the  spindles  feed  down  and  return  together. 

To  obtain  efficient  results  in  the  performance  of  drilling 
operations,  the  keynote  of  success  in  securing  a  satisfactory 
rate  of  production  is  often  found  in  a  satisfactory  solution  of 
the  problem  of  properly  balancing  the  ratio  of  drilling  time  to 
setting-up  time.  If  proper  means  are  not  provided  to  reduce 
setting-up  time,  this  will  often  become  so  excessive  that  the 
production  of  the  machine  is  far  below  the  normal  rate  which 
ought  to  be  secured.  For  work  where  there  are  a  large  number 

28 


MULTIPLE-SPINDLE  DRILLING  MACHINES  29 

of  holes  to  be  drilled,  profitable  use  may  be  made  of  multiple- 
spindle  drilling  machines.  These  are  built  with  different  num- 
bers of  spindles,  arranged  in  a  "  cluster,"  and  furnished  with 
the  necessary  adjustment  to  enable  the  spindles  to  be  set  in  the 
desired  positions  for  drilling  different  groups  of  holes.  The 
possibility  of  drilling  a  number  of  holes  simultaneously,  after 
setting  up  the  work  once,  is  obviously  the  means  of  greatly  in- 
creasing the  productivity  of  the  machine. 

Multiple  Drilling  Machines  of  Straight-line  Type.  —  In  con- 
nection with  the  introductory  statement  concerning  the  classes 
of  work  handled  on  multiple-spindle  drilling  machines  of  the 
straight-line  type,  mention  was  made  of  the  fact  that  such 
machines  are  commonly  employed  for  either  simultaneously 
drilling  a  number  of  holes  located  in  a  straight  line  in  a  piece  of 
work,  or  else  that  the  machines  are  arranged  to  perform  a  se- 
quence of  operations  on  parts  which  are  set  up  successively 
under  the  different  spindles  of  the  machine.  In  the  latter  case, 
the  operator  moves  progressively  from  spindle  to  spindle,  re- 
moving drilled  pieces  and  substituting  blanks  in  their  place 
ready  to  be  drilled. 

Fig.  i  shows  a  special  multiple-spindle  machine  of  the 
straight-line  type  built  for  the  Willys-Overland  Co.  by  the 
Foote-Burt  Co.,  which  is  engaged  in  the  performance  of  drill- 
ing operations  on  connecting-rods.  Here  the  work  is  of  such 
character  that  two  spindles  are  required  for  drilling  each  piece, 
but  the  length  of  these  operations  is  sufficient  so  that  a  four- 
spindle  machine  may  be  employed  to  allow  the  operator  to  busy 
himself  setting  up  work  under  one  pair  of  spindles,  while  the 
other  pair  is  engaged  on  the  drilling  operation  on  another  part. 
In  this  way  the  operator  is  kept  constantly  employed.  The 
work-holding  fixtures  used  on  this  machine  employ  two  prin- 
ciples which  are  often  used  in  jig  and  fixture  design  for  locating 
and  securing  the  work  in  place.  The  small  end  of  the  con- 
necting-rod is  pushed  into  a  V-block,  which  locates  it  under  the 
drill,  and  after  this  has  been  done,  a  bell-mouthed  bushing, 
through  which  the  other  drill  operates,  is  screwed  down  onto 
the  large  end  of  the  connecting-rod,  thus  locating  this  end  in 


MODERN  DRILLING  PRACTICE 


place  to  be  drilled  and  also  clamping  the  work  in  the  fixture. 
With  an  arrangement  of  this  kind  the  time  involved  in  setting 
up  the  work  is  reduced  to  a  point  where  lost  time  becomes  un- 
important. The  material  to  be  drilled  is  drop-forgings,  the 
large  hole  being  2.188  by  1.688  inch  deep;  and  the  small  hole  is 
1.123  by  iT5e  inch  deep.  The  operation  is  performed  at  a  speed 
of  325  revolutions  per  minute  and  a  feed  of  0.005  mch  per 


Fig.  i.     Four-spindle  Drilling  Machine  engaged  in  simultaneously 
drilling  Both  Holes  in  Two  Connecting-rods 

revolution;  the  production  is  720  crankshafts  per  eight-hour  day 
from  each  machine. 

For  use  in  drilling  and  tapping  nose  adapters  for  shrapnel 
cases,  excellent  results  have  been  obtained  with  an  equipment 
consisting  of  two  four-spindle  drilling  machines  built  by  the 
Washburn  Shops.  These  machines  are  of  the  power-feed  type 
and  are  placed  back  to  back,  as  shown  in  Fig.  2,  with  metal 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


covered  shelves  extending  across  the  ends  of  the  machines  to 
provide  for  sliding  jigs  from  one  machine  to  the  other.  The 
work  consists  of  drilling  two  holes,  each  of  which  must  subse- 
quently be  tapped,  the  sizes  being  f-  and  y^-inch  tap  holes. 
The  interesting  feature  of  this  installation  is  the  careful  way  in 
which  plans  were  made  to  increase  production  as  far  as  possible. 
About  three  dozen  jigs  were  supplied  and  the  "  team  "  which 
operates  this  pair  of  machines  consists  of  ten  operatives3  one  at 


Fig.  2.     Battery  of  Two  Four-spindle  Drilling  Machines  operated  by 
"  Team  "  of  Ten  Men  for  Drilling  and  Tapping  Holes  in  Fuse  Parts 

each  of  the  spindles  and  one  stationed  at  each  end  shelf,  whose 
duty  it  is  to  remove  finished  pieces  from  the  jigs  and  substitute 
fresh  blanks.  A  piece  is  placed  in  a  jig  by  one  of  the  men  sta- 
tioned in  the  loading  position,  and  this  piece  is  passed  along 
from  spindle  to  spindle,  so  that  the  two  holes  are  drilled  and 
tapped  by  the  four  spindles  of  one  machine  unit.  This  piece  is 
then  removed  from  the  jig  and  a  fresh  blank  substituted,  after 
which  the  jig  is  pushed  across  the  shelf  to  the  four  men  operating 
the  machine  at  the  opposite  side  of  the  group.  In  this  way, 
each  jig  goes  round  and  round  in  a  continuous  circuit,  and  there 
is  practically  no  loss  of  time.  The  order  in  which  the  operations 


32  MODERN  DRILLING  PRACTICE 

are  performed  is  as  follows:  Drill  f-inch  hole,  drill  y3g- inch  hole; 
tap  f-inch  hole  and  tap  T3g-inch  hole.  These  men  work  ten 
hours  a  day  on  a  piece-work  basis,  and  the  normal  rate  of  pro- 
duction is  about  5500  pieces  per  working  day  for  each  gang. 
At  times  the  production  was  increased  to  a  considerable  extent, 
but  this  is  regarded  more  in  the  light  of  a  "  spurt  "  than  normal 
operating  conditions. 

Sliding  Jigs  for  Multiple-spindle  Operation.  —  In  the  plant 
of  the  Hupp  Motor  Car  Co.,  heavy-duty  drilling  machines, 
built  by  the  Colburn  Machine  Tool  Co.,  are  used  for  drilling 
and  reaming  connecting-rods.  A  gang  of  four  machines  is  used 


Fig.  3.  Gang  of  Four  High-duty  Drilling  Machines  equipped  with  Sliding 
Jigs  for  Drilling  Connecting-rods.  One  Spindle  is  held  in  Reserve  to 
Substitute  as  required 

equipped  with  a  special  combination  table  or  track  on  which  the 
jigs  are  slid  along  from  one  spindle  to  another,  the  arrangement 
being  clearly  shown  in  Fig.  3.  Looking  at  the  spindles  from 
right  to  left,  the  first  spindle  at  the  right  drills  out  the  hole  at 
the  large  end  of  the  connecting-rod  and  the  second  spindle  reams 
this  hole;  the  third  is  a  reserve  spindle,  the  use  of  which  will  be 
explained  later,  and  the  fourth  spindle  drills  the  hole  in  the 
small  end  of  the  connecting-rod.  One  operator  attends  to  the 
whole  battery  of  machines,  and  after  he  has  started  a  drill 
working  on  one  hole,  he  goes  along  to  the  next  jig  and  gets 
it  ready  for  operation.  The  jigs  are  never  lifted,  it  being  merely 
necessary  for  the  operator  to  remove  the  drilled  connecting-rod 
and  insert  a  new  forging  after  each  operation. 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


33 


By  having  the  drilling  machines  independently  belted,  it  is 
possible  to  obtain  any  speed  for  any  particular  requirement,  and 
should  a  break-down  occur  on  any  spindle,  the  other  three 
spindles  are  not  affected,  as  would  be  the  case  with  a  multiple- 
spindle  machine  of  the  straight-line  type.  In  case  of  emergency, 
the  reserve  spindle  may  be  quickly  changed  over  to  either  tool 
that  requires  this  spindle,  so  that  production  is  not  held  up. 
The  way  in  which  the  connecting-rods  are  held  in  the  jigs  is 


Fig.  4.     Vertical  Drilling  Machines  with  Multiple  Heads 

apparent  from  the  illustration.  Both  ends  of  the  rod  rest  on 
finished  pads  in  the  jig,  and,  by  tightening  the  clamping  screw, 
the  large  end  of  the  rod  is  forced  between  the  ends  of  two  con- 
verging studs  that  form  the  equivalent  of  a  V-block.  The 
clamping  screw  is  inclined  slightly  downward  so  that  it  holds  the 
work  down  on  the  supporting  surfaces  of  the  jig.  The  drop- 
forgings  to  be  drilled  contain  from  0.035  to  °-°45  Per  cent  of 
carbon.  The  hole  to  be  drilled  in  the  large  end  of  the  rod  is 
2^  inches  in  diameter  by  if  inch  deep;  and  the  hole  in  the 
small  end  of  the  rod  is  0.864  inch  in  diameter  by  f  inch  deep. 


34 


MODERN  DRILLING  PRACTICE 


The  rate  of  production  secured  on  this  job  is  400  connecting- 
rods  in  a  nine-hour  working  day. 

Vertical  Machines  equipped  with  Multiple-spindle  Drill 
Heads.  —  Fig.  4  shows  an  installation  of  vertical  drilling  ma- 
chines built  by  the  Rockford  Drilling  Machine  Co.,  and  equipped 
with  multiple-spindle  drill  heads.  The  feature  of  this  equip- 
ment is  the  provision  of  a  jig-plate  carried  by  the  drill  head,  as 
shown  in  detail  in  Fig.  5,  which  gives  a  view  of  the  jig  con- 
struction. This  jig-plate  comes  down  to  the  points  of  the  drills, 
so  that  adequate  support  is  provided  during  the  intervals  at 


Machinery 


Fig.  5.  Multiple-spindle  Drill  Head  provided  with  Jig-plate  that  is 
Lifted  with  Head  when  Spindle  of  Drilling  Machine  Rises  in 
Order  to  Facilitate  Removal  of  Work  from  Fixture 

which  the  drills  are  being  started  into  the  work;  then  the  jig- 
plate  remains  on  the  work  while  the  drills  are  fed  in  to  the 
desired  depth.  While  the  drilling  machine  spindle  is  raised, 
the  head  carries  the  jig-plate  up  with  it,  so  that  there  is  no 
obstruction  to  hinder  the  operator  in  removing  work  from 
the  fixture.  The  way  in  which  this  result  is  secured  is  as  follows : 
When  the  drilling  machine  spindle  is  raised,  heads  at  the  lower 
ends  of  rods  A,  carried  by  the  multiple  head,  lift  the  jig-plate. 
These  arms  are  so  adjusted  that  the  jig-plate  is  held  with  its 


MULTIPLE-SPINDLE  DRILLING  MACHINES  35 

lower  surface  just  above  the  drill  points,  as  shown  in  Fig.  4. 
When  the  drills  are  fed  down  to  the  work,  the  jig-plate  drops 
until  further  movement  is  retarded  by  flanges  on  rods  B  carried 
by  the  work-holding  fixture.  In  this  position,  the  jig  continues 
to  support  the  drills,  but  the  drills  may  be  fed  through  to  the 
desired  depth.  It  will  be  apparent  that  jig-plate  C  is  furnished 
with  the  usual  arrangement  of  hardened  steel  bushings ;  and  the 
work  is  held  in  the  fixture  by  an  arrangement  of  clamps  as 
shown  in  the  illustration.  The  drill  heads  shown  on  the  ma- 
chines in  Fig.  4  are  of  four-  and  eight-spindle  types,  respectively, 
and  the  work  to  be  drilled  consists  of  two  types  of  universal 
joint  rings.  The  holes  drilled  by  the  four-spindle  head  are  T5g 
inch  in  diameter  by  f  inch  deep,  and  the  holes  drilled  by  the 
eight-spindle  head  are  T5g  inch  in  diameter  by  J  inch  deep.  The 
material  is  drop-forgings  containing  from  0.025  to  0.035  Per  cent 
of  carbon.  The  rate  of  production  is  from  1400  to  1500  rings  in 
a  ten-hour  working  day. 

Compressed  Air  for  Ejecting  Work  from  Fixtures.  —  Mention 
has  already  been  made  of  the  increased  importance  of  designing 
fixtures  to  provide  for  the  rapid  handling  of  work  on  account  of 
the  reduction  in  drilling  time  which  has  been  made  possible 
through  the  design  of  high-speed  machines.  Fig.  6  shows  the 
fixture  used  on  a  machine  equipped  with  a  two-spindle  head 
which  is  used  for  drilling  holes  0.107  incn  m  diameter  in  disks 
shown  at  A.  A  feature  of  this  equipment  is  the  provision  for 
rapid  handling  of  the  work.  A  supply  of  disks  is  kept  in  feed- 
trough  B,  and  as  soon  as  one  piece  has  been  engaged  by  the 
drills,  the  operator  lays  his  thumb  on  a  second  piece  and  starts 
to  advance  it  to  the  drilling  position.  Location  of  the  work  is 
very  simple,  as  it  is  merely  necessary  to  slide  the  work  into  the 
notch  C,  which  locates  it  under  the  drill  spindles.  When  the 
drilling  operation  has  been  completed,  the  operator  removes  his 
thumb  from  the  piece  of  work  and  reaches  for  another  piece. 
As  the  spindle  on  the  machine  rises,  a  blast  of  compressed  air 
through  tube  D  blows  the  drilled  work  off  the  fixture  and  it 
drops  through  opening  E  into  a  receiver.  At  the  back  of  the 
drill  head  is  located  a  stud  F  that  engages  a  trip  which  actuates 


MODERN  DRILLING  PRACTICE 


air-valve  G  to  provide  for  the  admission  of  air  into  tube  D  at 
the  proper  time  to  eject  the  work.  Such  an  apparatus  may  be 
worked  very  rapidly. 

Multiple-spindle  Drilling  Machines  of  Cluster  Type.  —  Ma- 
chines which  will  be  discussed  under  this  heading  may  be  roughly 
subdivided  into  standard  and  special  equipments.  Standard 
multiple-spindle  drilling  machines  are  built  by  several  firms  and 
are  practically  universal  in  their  application,  in  so  far  as  drilling 
holes  over  an  area  within  their  range  is  concerned.  The  only 


.Machinery 


Fig.  6.  Work-holding  Fixture  provided  with  Automatically-operated 
Air  Ejector  to  Discharge  Work  through  Chute  into  Receiver 
placed  under  Drilling  Machine 

limitation  in  the  use  of  these  machines  is  in  regard  to  the  min- 
imum distance  between  centers  of  different  holes  that  must  be 
drilled.  As  compared  with  this  condition,  there  is  the  special- 
purpose  multiple-spindle  drilling  machine  which  is  adapted  for 
the  performance  of  one  specific  manufacturing  operation;  ma- 
chines of  this  type  are  being  used  to  good  advantage  in  the 
performance  of  drilling  operations  on  automobile  crankcases, 
etc.,  but  it  necessarily  follows  that  a  plant  that  can  afford  to 
buy  a  single-purpose  multiple-spindle  drilling  machine  must 


MULTIPLE-SPINDLE   DRILLING  MACHINES 


37 


have  a  large  volume  of  work  in  order  to  be  able  to  earn  a  fair 
return  upon  the  investment.  After  reading  the  following 
description  of  operations  performed  on  machines  of  each  type, 


Fig.  7. 


Ten-spindle  Drilling  Machine  engaged  in  drilling  and 
reaming  Rear  Axle  Spiders 


the  reader  will  have  a  good  idea  of  the  scope  of  work  that  comes 
within  the  province  of  the  cluster-type  multiple-spindle  drilling 
machine. 


38  MODERN  DRILLING  PRACTICE 

Indexing  Fixture  on  Machine  of  Cluster  Type.  —  Fig.  7  shows 
one  of  the  No.  14  "  Natco  "  multiple-spindle  drilling  machines 
built  by  the  National  Automatic  Tool  Co. ;  this  machine  is  used 
at  the  plant  of  the  Willys-Overland  Co.  for  drilling  and  reaming 
one  hole  f  inch  in  diameter  by  if  inch  deep  and  two  holes  f  inch 
in  diameter  by  i  inch  deep;  in  addition,  four  ^J-inch  holes, 
3^  inch  deep,  are  drilled  in  the  flange  of  the  rear  axle  spiders, 
but  these  holes  are  not  reamed.  This  installation  is  somewhat 
exceptional  in  that  it  involves  the  use  of  an  indexing  fixture  on  a 
multiple-spindle  drilling  machine.  This  fixture  is  furnished  with 
three  stations,  one  of  which  is  a  loading  station;  at  one  station, 
the  three  large  holes  are  drilled  and  two  of  the  |  J-inch  holes  are 
also  drilled,  and  at  the  third  station,  the  three  large  holes  are 
reamed  while  the  other  two  J|-inch  holes  are  drilled.  Evidently 
this  calls  for  the  use  of  a  ten-spindle  drilling  machine  with  the 
spindles  arranged  in  two  groups  of  five  spindles  each.  In  the 
first  group  there  are  one  f-inch  drill,  two  f-inch  drills,  and  two 
J|-inch  drills;  in  the  second  group,  there  are  one  f-inch  reamer, 
two  f-inch  reamers,  and  two  -J|-inch  drills.  The  arrangement 
of  these  holes  in  the  work  will  be  apparent  after  studying  the 
piece  shown  lying  at  the  base  of  the  machine  just  under  the 
fixture.  The  f-inch  hole  is  shown  at  A,  the  two  f-inch  holes  at 
B,  and  the  four  |J-inch  holes  at  C. 

The  preceding  description  has  explained  the  manner  in  which 
the  indexing  fixture  carries  the  work  under  the  two  groups  of 
spindles,  in  order  to  provide  for  drilling  and  reaming  three 
holes  and  drilling  four  other  small  holes.  The  arrangement  of 
this  work-holding  fixture  is  quite  interesting.  A  pilot  carried 
on  pivoted  bar  D  enters  the  hole  in  the  lower  end  of  the  work 
and  raises  the  work  so  that  a  pilot  carried  by  frame  E  enters  the 
upper  end.  After  the  pivoted  bar  D  has  been  clamped  by  T- 
screw  F,  the  work  is  secured  in  the  fixture,  as  regards  its  vertical 
position.  It  is  still  necessary,  however,  to  locate  the  work 
about  its  vertical  axis  so  that  all  seven  holes  A ,  B,  and  C  will  be 
properly  positioned  in  the  spider.  This  is  accomplished  by  a 
sliding  V-block,  which  is  pushed  over  the  end  of  the  work  ad- 
jacent to  the  f-inch  hole  A  by  means  of  screw  G. 


I 

H 
06 


39 


40  MODERN  DRILLING  PRACTICE 

There  are  three  complete  sets  of  mechanism  corresponding  to 
each  of  the  three  stations  on  the  work-holding  fixture,  and  for 
each  traverse  of  the  multiple-spindle  drill  head,  one  spider  is 
finished,  so  that  the  operator  may  remove  one  piece  at  the  load- 
ing station  and  substitute  a  fresh  blank.  These  spiders  are 
made  of  malleable  iron  and  the  rate  of  production  is  960  pieces 
per  eight-hour  working  day.  Owing  to  the  length  of  time 
required  to  load  pieces  into  this  fixture,  the  speed  and  feed  at 
which  the  operation  is  performed  are  less  than  would  ordinarily 
be  employed  for  drills  and  reamers  of  these  sizes.  This  loss  is 
partially  offset  by  the  fact  that  more  parts  are  obtained  for  each 
grinding  of  the  tools. 

Traveling  Jigs  used  in  Conjunction  with  Machines  of  the 
Cluster  Type.  —  At  the  plant  of  the  Continental  Motors  Co., 
there  is  an  interesting  equipment  of  multiple-spindle  drilling 
machines  built  by  the  Baush  Machine  Tool  Co.  These  machines 
are  used  for  the  performance  of  drilling  operations  on  the  engine 
cylinder  blocks,  and  to  facilitate  handling  of  the  work  as  far  as 
possible  an  interesting  arrangement  of  traveling  jigs  has  been 
developed.  Reference  to  Fig.  8  will  show  that  each  of  these 
fixtures  is  carried  on  a  truck  running  on  tracks  that  pass  along 
under  the  heads  of  the  multiple-spindle  drilling  machines.  The 
jigs  are  supported  on  trunnions  in  the  truck  frames,  which 
make  it  possible  to  swing  the  work  around  to  provide  for  the 
performance  of  drilling  operations  in  different  planes  on  the 
work.  Each  drilling  machine  is  equipped  with  a  cluster  head  in 
which  the  spindles  are  grouped  to  provide  for  simultaneously 
drilling  all  of  the  holes  in  one  face  of  the  cylinder  block.  After 
the  groups  of  small  holes  have  been  drilled,  the  work  goes  on 
under  straight-line  multiple-spindle  drilling  machines  which 
provide  for  drilling  the  valve-stem  holes,  valve  push-rod  holes, 
etc.  The  work  is  then  removed  from  the  jig  and  the  empty 
truck  is  run  onto  a  section  of  track,  which,  in  turn,  is  supported 
on  truck  wheels  so  that  the  track  may  be  moved  over  into 
alignment  with  the  return  track  rails,  which  will  be  seen  in  the 
foreground  of  the  picture.  As  the  truck  jig  moves  down  this 
track  a  new  casting  is  put  in  place,  after  which  the  jig  is  moved 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


along  onto  a  second  transfer  truck  on  which  it  is  moved  over  to 
the  rails  which  will  carry  it  under  the  drilling  machines  for  the 
performance  of  successive  operations.  With  this  arrangement, 


Fig.  9.  Multiple-spindle  Drilling  Machine  equipped  with  Sliding 
Fixture  to  Facilitate  Loading  Casting  in  Fixture  and  Remov- 
ing Drilled  Work 

it  is  possible  to  employ  a  sufficient  number  of  reserve  jigs,  so 
that  work  may  be  constantly  available  for  the  machines  as  fast 
as  they  complete  operations  on  a  given  cylinder  block.  Conse- 


42 


MODERN  DRILLING  PRACTICE 


quently,  idle  time  of  the  machines  and  operators  is  reduced  very 
close  to  the  absolute  minimum. 

Sliding  Fixture  applied  to  Machine  of  the  Cluster  Type.  — 
Fig.  9  shows  another  application  of  a  Baush  multiple-spindle 
drilling  machine  on  cylinder  block  work.  In  this  case,  the  ma- 
chine is  employed  in  the  plant  of  the  Lozier  Motor  Co.,  and  the 
arrangement  of  the  work-holding  fixture  and  the  jig-plate  brings 


Fig.  ID.     Three-way  Multiple-spindle  Drilling  Machine  for  Drilling 
Eighty-four  Holes  in  Automobile  Crankcase  at  One  Setting 

out  two  principles  which  are  of  interest.  In  the  first  place, 
the  base  A ,  on  which  the  work  is  supported,  is  mounted  on  ways 
which  enable  it  to  be  slid  out  from  under  the  multiple-spindle 
drill  head  to  provide  for  the  convenient  removal  of  drilled  work 
and  the  substitution  of  a  fresh  casting.  The  other  point  of  in- 
terest in  connection  with  this  work  is  the  use  of  a  jig-plate  J5, 
which  is  secured  to  the  work  to  provide  for  maintaining  a  posi- 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


43 


live  relation  of  the  drills  to  one  another.  This  idea  of  employ- 
ing a  jig-plate  which  is  secured  to  the  work,  instead  of  having 
the  jig  part  of  a  work-holding  fixture  which  carries  the  piece  to 
be  drilled,  may  be  employed  in  many  cases  with  very  satis- 
factory results. 

Special    Multiple-spindle    Machines.  —  In   addition   to   the 
universal  multiple-spindle  machines  previously  described,  there 


Fig.  ii.     Multiple  Drilling  Machines  used  in  Couples  for  Drilling,  Reaming, 
and  Counterboring  Holes  in  Floor-plate  of  Rifle  Receivers 

is  a  very  important  group  of  cluster-type  multiple-spindle 
drilling  machines  which  are  designed  and  built  to  meet  the 
requirements  of  specific  manufacturing  operations.  In  these 
machines  the  spindles  are  not  usually  made  adjustable,  because 
they  are  intended  for  one  given  class  of  work,  and  each  spindle 
is  properly  located  to  drill  the  particular  hole  in  the  work  for 
which  that  spindle  has  been  provided.  Fig.  10  shows  a  three- 
way  multiple-spindle  drilling  machine  built  by  the  Foote-Burt 


44 


MODERN  DRILLING  PRACTICE 


Co.  for  use  in  simultaneously  drilling  all  of  the  screw  holes  in  the 
upper  half  of  a  Willys-Overland  crankcase.  The  material  is 
aluminum,  and  this  machine  provides  for  drilling  eighty-four 
holes  at  a  single  setting  of  the  work.  An  idea  of  the  remarkable 
rate  of  production  secured  through  the  possibility  of  simul- 
taneously drilling  such  a  large  number  of  holes  will  be  gathered 
from  the  fact  that  480  crankcases  are  drilled  in  an  eight-hour 
working  day.  This  machine  is  so  designed  that  the  different 


^COUNTERBORE    0.275 

/    REAM    0.178" 
-r-£       /^     A 


6.1  M.M.   DRILL  0.2008 
COUNTERBORE   0.315" 
REAM   0.178"^ 


0.8071" 
0.811" 


0.5079 
0.5118 


1A  'DRILL 


'DRILL 


Machinery 


Fig.  12.     Rifle  Receiver  Floor-plate  which  is  drilled,  reamed,  and 
count erbored  in  Machines  shown  in  Fig.  n 

sizes  of  drills  are  driven  at  approximately  the  correct  speed  and 
feed. 

Special-purpose  multiple-spindle  drilling  machines  of  the 
cluster  type  are  built  for  a  great  variety  of  work,  although  the 
automobile  industry  represents  the  most  important  field  in 
which  these  machines  are  employed.  The  reason  for  this  is 
that  it  would  not  pay  to  invest  in  an  expensive  machine  of  this 
kind,  unless  the  volume  of  work  to  be  drilled  were  sufficiently 
great  so  that  it  would  be  found  profitable  to  build  special  ma- 
chines for  handling  the  work.  Among  the  parts  which  are 
frequently  drilled  on  special-purpose  multiple-spindle  drilling 
machines,  the  following  may  be  mentioned:  cylinder  blocks, 
transmission  cases,  flywheels,  crankcases,  crankshafts,  differ- 
ential frames,  wheel  hubs,  cover  plates,  etc. 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


45 


Drilling,  Reaming,  and  Counterboring  on  Multiple-spindle 
Machines.  —  Fig.  n  shows  two  Langelier  multiple  drilling  ma- 
chines used  in  couples  for  drilling,  reaming,  and  counterboring 
four  holes  in  the  floor-plate  of  a  foreign  rifle.  The  operations 
are  performed  without  removing  the  work  from  the  jig.  The 
drilling  is  done  with  the  machine  at  the  left  in  two  operations, 
and  the  reaming  and  counterboring  with  the  machine  at  the 
right  in  two  operations.  Fig.  12  shows  the  floor-plate.  Three 
of  the  holes  are  drilled,  reamed,  and  counterbored ;  the  fourth  is 
only  drilled.  The  holes  are  drilled  half  way  through  from  each 


Machinery 


Fig.   13.     Lay-out   of   Spindles  in     Fig.    14.     Lay-out    of   Spindles  in 
Drilling  Head  Reaming  and  Counterboring  Head 


side,  the  meeting  of  holes  not  being  important,  as  the  floor-plate 
is  afterward  slotted  as  shown  by  the  dotted  lines.  To  produce 
the  greatest  possible  output  from  these  machines,  an  operator 
is  required  for  each  machine,  while  a  third  loads  and  unloads 
the  jigs.  A  set  of  three  jigs  is  used;  thus  the  machines  are 
continually  at  work.  Fig.  13  shows  the  lay-out  of  spindles  in 
the  drilling  head  for  the  two  drilling  operations.  This  head  is 
in  the  machine  to  the  left  in  Fig.  n.  The  group  of  four  spindles 
that  carry  the  5.1 -millimeter  and  the  three  No.  17  drills  is  used 
for  the  first  operation  with  the  cover  side  of  the  jig  down.  The 
four  that  carry  the  5.1 -millimeter  and  the  three  |-inch  drills  are 
used  for  the  second  operation  with  the  cover  side  up.  The 


MODERN  DRILLING  PRACTICE 


|-mch  holes  are  not  reamed.     The  jig  is  then  carried  to  the 
second  machine. 

Fig.  14  shows  the  lay-out  of  spindles  in  the  drilling  head  in  the 
machine  to  the  right  in  Fig.  u,  which  is  used  for  reaming  and 
counterboring.  The  group  of  three  spindles  carrying  the  0.178- 
inch  reamers  does  the  reaming  with  the  cover  side  of  the  jig  down. 
The  group  of  spindles  carrying  the  two  0.2 7  5-inch  and  one 


Machinery 


Fig.  15.  Partial  Side  Elevation  of  Drill  Head  used  on  Machine  at 
Left  in  Fig.  u,  showing  Sub-jig  and  Jig  in  Position  for  First 
Drilling  Operation 

0.3 1 5-inch  counterbores  does  the  counterboring  with  the  cover 
side  of  the  jig  down. 

Fig.  15  is  a  partial  side  elevation  showing  the  drill  head  with 
its  sub-jig  attached  and  the  jig  on  the  table  of  the  machine  in 
position  for  the  first  drilling  operation.  The  sub- jigs  on  the  two 
machines  are  the  same  in  principle.  The  bushings  in  the  sub-jig 
guide  the  tools,  and  the  bushings  in  the  jig  guide  the  sub-jig, 


MULTIPLE-SPINDLE  DRILLING  MACHINES  47 

By  this  method,  each  of  the  drills,  reamers,  or  counterbores  has 
its  own  guide  bushing,  and  the  use  of  interchangeable  slip  bush- 
ings in  the  jig  is  avoided.  The  sub- jig  is  attached  to  the  drill 
head  under  the  compression  of  a  spring.  When  the  sub-jig 
comes  in  contact  with  the  work  jig,  it  is  forced  upward  while  the 
drilling,  reaming,  or  counterboring  takes  place.  The  sub-jigs 
can  be  quickly  removed  by  unscrewing  two  tapering  thumb-pins 
so  as  to  provide  free  access  to  the  tools,  if  required.  All  of  the 
spindles  are  provided  with  adjusting  screw  collets  so  as  to  com- 
pensate for  the  grinding  of  tools,  also  for  individual  adjustment 
for  depth  of  holes.  The  jigs  are  of  the  swing  cover  type,  com- 
pensating means  and  stops  being  incorporated  for  accurately 
locating  and  holding  the  work  while  it  is  operated  upon.  The 
machines  are  of  the  round  column  and  base  type.  The  table 
has  a  working  surface  of  21  by  14  inches,  which  is  ample  for  the 
handling  of  the  jigs.  It  is  trunnioned  into  a  supporting  arm 
that  is  clamped  to  the  column  and  can  be  adjusted  to  the  re- 
quired working  position.  The  trunnion  of  the  table  has  a  rack 
which  meshes  with  a  pinion  shaft  having  bearings  in  the  sup- 
porting arm  and  to  which  is  attached  the  long  feed  hand-lever/ 
A  single  feed-stop  is  provided  for  the  table  for  both  operations. 

Station-type  Multiple-spindle  Drilling  Machines.  —  The  bat- 
tery of  Baush  multiple-spindle  drilling  machines  shown  in  Fig.  8 
is  used  in  conjunction  with  a  traveling  jig  as  previously  described, 
which  carries  the  work  from  one  machine  to  another  in  order 
that  advantage  may  be  taken  of  the  possibility  of  performing  a 
number  of  groups  of  operations  without  the  necessity  of  resetting 
the  work.  When  the  importance  of  the  savings  that  are  pos- 
sible through  the  use  of  such  an  arrangement  has  been  fully 
appreciated,  it  will  be  apparent  that  a  still  further  benefit  would 
be  secured  by  the  combination  of  different  groups  of  spindles  in 
a  single  machine  that  would  provide  for  saving  time  by  avoid- 
ing the  necessity  of  frequent  resetting  of  the  work,  and  at  the 
same  time  economizing  in  floor  space  through  having  the  entire 
outfit  contained  in  a  single  unit.  This  is  the  idea  that  has  been 
successfully  accomplished  through  development  of  the  "  station 
type  "  of  multiple-spindle  drilling  machines  which  are  built  by 


MODERN  DRILLING   PRACTICE 


the  Baush  Machine  Tool  Co.  Machines  of  this  type  were  first 
constructed  for  the  use  of  the  Ford  Motor  Co.  in  drilling  all  of 
the  holes  that  are  required  in  flywheel  castings.  The  corn- 


Fig.  1 6.     Station-type  Multiple-spindle  Drilling  Machine  built  for 
Performing  Eighty-one  Drilling,   Counterboring,   and  Ream-      ' 
ing  Operations  on  Ford  Flywheels 

plete  machine  for  doing  this  work  is  shown  in  Fig.  16,  and  Figs.  17 
to  19,  inclusive,  show,  respectively,  the  loading  station  where 


MUI/IIPLE-SPINDLE  DRILLING  MACHINES  49 

the  work  is  set  up  on  tlio  machine,  a  view  of  two  multiple- 
spindle  drill  heads,  and  a  view  of  heads  equipped  with  tools  for 
the  performance  of  drilling  and  reaming  operations. 

In  operating  the  machine,  each  flywheel  is  placed  on  a  sup- 
porting block  and  secured  by  means  of  an  expanding  center. 


Fig.  17.     View  of  Loading  Station  of  Drilling  Machine  shown 
in  Fig.   1 6 

The  loading  station  on  the  machine  is  illustrated  in  Fig.  17, 
and  in  this  view  the  wrench  used  for  expanding  the  center  on 
which  the  flywheel  is  held  will  be  clearly  seen  in  position.  The 
counterbore  in  the  wheel  is  used  to  locate  the  work  under  each 
jig,  this  result  being  obtained  by  a  tapered  leader  which  enters 
the  counterbore  as  the  jig  at  each  station  on  the  machine  comes 


50  MODERN  DRILLING  PRACTICE 

I 

down  to  the  working  position.  In  a^ditigtf  to  this  counterbore, 
there  is  a  flat  dowel  in  the  supporting  block  that  registers  be- 
tween two  jaws  on  the  extreme  outside  portion  of  the  jig,  thus 
securing  the  wheel  against  rotation.  The  feed  is  accomplished 
by  means  of  a  barrel  cam  which  is  of  the  correct  form  to  give  a 
quick  approach  and  the  desired  rate  of  feed  and  return.  By 


Fig.  1 8.     Close  View  of  Multiple-spindle  Drill  Heads 

employing  different  cams,  suitable  rates  of  feed  may  be  em- 
ployed for  the  tools  in  different  heads.  The  table  is  rotated  by 
a  mechanism  which  also  lifts  it,  thus  allowing  the  weight  to  be 
carried  on  a  center  pintle,  while  it  is  in  motion,  and  the  pro- 
vision of  ball  bearings  in  this  connection  makes  it  possible  for 
the  table  to  be  easily  moved.  A  hardened  steel  locking  bolt  is 


MULTIPLE-SPINDLE  DRILLING  MACHINES  51 

provided,  which  is  actuated  by  a  cam  and  comes  into  play  just 
before  the  table  is  lowered  to  its  working  position,  where  the 
bolt  locks  the  table  in  place. 

When  in  the  working  position,  the  table  rests  on  a  circular 
rail  which  is  slightly  smaller  than  its  outside  diameter,  this  rail 


Fig.  19.     Drill  Heads  equipped  with  Tools  for  Drilling  and 
Reaming  Operations 

being  carried  up  inside  a  flange  at  the  periphery  of  the  table  to 
protect  the  bearing  from  chips.  One  central  oiling  system  is 
provided  which  delivers  lubricant  to  all  bearings,  the  pump 
taking  the  oil  from  a  tank  in  the  base  and  circulating  it  through 
a  system  of  piping  provided  with  return  connections.  There 
are  eighty-one  drilling,  couriterboring,  and  reaming  operations 


52  MODERN  DRILLING  PRACTICE 

to  be  performed  on  the  Ford  flywheel,  and  with  this  machine  it 
is  found  possible  to  perform  all  of  these  operations  in  fifty-four 
seconds.  Each  machine  has  a  capacity  for  drilling  500  fly- 
wheels in  an  eight-hour  working  day,  the  actual  rate  of  produc- 
tion being  510  flywheels  in  450  minutes. 

The  operations  consist  of  drilling  sixteen  ||-inch  holes  in  the 
inner  circle  through  i|  inch  of  metal,  and  sixteen  J-inch  holes 
in  the  outer  circle  half  way  through  the  same  thickness  of  metal; 
second,  counterboring  the  sixteen  holes  in  the  inner  circle  to  a 
diameter  of  0.386  by  T%  inch  deep,  and  drilling  the  holes  in  the 
outer  circle  through  the  remaining  metal,  a  o.2O4-inch  drill 
being  used  for  this  purpose  which  cuts  through  T7g  inch;  third, 
counterboring  three  half  round  faces  0.936  inch  in  diameter  by 
f  inch  deep  in  the  hub  of  the  wheel;  fourth,  drilling  four  holes 
0.386  by  |  inch  deep,  two  holes  f  £  by  f  inch  deep,  and  three 
holes  f  J  by  J  inch  deep;  fifth,  reaming  three  holes  0.675  mcn  m 
diameter  by  J  inch  deep  and  two  holes  0.436  inch  in  diameter 
by  f  inch  deep. 

While  the  discussion  of  the  work  of  this  machine  is  presented 
in  connection  with  its  application  in  machining  the  flywheels  of 
Ford  motor  cars,  it  must  not  be  thought  that  this  is  a  single- 
purpose  machine,  because  there  are  a  great  many  classes  of 
work  that  could  be  handled  on  an  equipment  of  this  type  with 
beneficial  results.  Not  only  is  the  use  of  this  machine  respon- 
sible for  saving  a  lot  of  space  in  the  shop,  but  it  will  be  appar- 
ent that  its  use  also  presents  the  possibility  of  drilling  holes  on 
centers  that  would  be  too  close  for  an  ordinary  multiple-spindle 
drilling  machine.  Where  the  center  distance  is  so  close  that  it 
would  be  impossible  to  arrange  spindles  in  a  cluster  head  to 
provide  for  drilling  them  with  a  machine  of  this  type,  one  hole 
may  be  drilled  by  one  head  and  the  next  hole  by  a  following 
head,  so  that  the  question  of  distance  from  center  to  center 
becomes  relatively  unimportant.  The  multiple-head  feature  also 
makes  it  possible  for  heavy  and  light  drills  to  be  grouped  together 
in  different  heads,  so  that  each  size  may  be  operated  at  suitable 
rates  of  cutting  speed  and  feed.  Different  standard  spindle 
clusters  may  be  furnished  to  meet  the  requirements  of  different 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


53 


classes  of  work,  and  these  heads  may  be  readily  removed  to 
enable  different  ones  to  be  substituted.     The  regular  ad  just- 


Fig.  20.     Station-type  Drilling  Machine  for  Drilling  Rifle  Bolts 
and  Receivers 

able  drill  heads  built  by  the  Baush  Machine  Tool  Co.  can  also  be 
used  to  adapt  the  machine  for  more  or  less  general  classes  of 


54  MODERN  DRILLING  PRACTICE 

multiple  drilling.  A  switch  and  starter  are  located  beside  the 
loading  station,  which  enable  the  operator  to  control  the  motor 
with  his  left  hand,  while  the  feed  mechanism  is  governed  by  a 
small  lever  at  the  right-hand  side  of  the  operating  position. 
By  means  of  this  lever,  it  is  possible  to  stop  all  the  feed  motions 
of  the  machine  instantly,  including  the  indexing  of  the  table. 
Station-type  Machine  equipped  with  Inverted  Drills.  —  The 
station-type  drilling  machine  shown  in  Fig.  20  was  designed 
and  built  by  the  Baush  Machine  Tool  Co.  for  drilling  the  bolts 
and  receivers  of  military  rifles.  At  first  sight,  this  machine 
may  appear  similar  to  the  preceding  type  for  drilling  automobile 
flywheels,  but  as  a  matter  of  fact  there  are  noteworthy  points  of 
difference.  On  the  preceding  type  of  machine  the  drills  are 
carried  in  multiple  heads  and  the  work  is  mounted  on  an  in- 
dexing table  supported  by  the  base  of  the  machine.  In  the 
present  case,  the  work  is  supported  in  fixtures  carried  by  the 
spindles  of  an  indexing  turret,  while  the  tools  are  carried  on  a 
fixed  spider.  In  both  cases,  the  drive  is  from  above,  but  in  the 
case  of  the  present  machine  the  work  revolves  and  the  tools 
remain  stationary.  Advantage  is  taken  of  the  inverted  drilling 
principle,  which  is  beneficial  in  clearing  chips  from  the  work. 
Feeding  the  drills  to  the  work  is  accomplished  by  raising  the 
spider  on  which  the  drills  are  carried.  The  drills  increase  pro- 
gressively in  length  in  order  to  obtain  the  required  depth  of  hole, 
and  it  will  be  evident  that  for  each  indexing  of  the  work  one 
finished  part  is  produced.  The  use  of  various  lengths  of  drills 
serves  the  same  purpose  as  backing  out  the  drill  at  the  required 
intervals,  which  is  the  practice  in  deep-hole  drilling  operations 
where  a  single  drill  is  employed.  On  this  machine  the  drills 
used  are  of  the  oil-tube  type,  which  provide  for  delivering  oil 
direct  tho  te  cutting  point  of  the  drill.  Drive  is  provided  by 
an  electric  motor  at  the  top  of  the  machine,  from  which  power  is 
transmitted  to  the  spindles  which  carry  the  work-holding  fix- 
tures by  means  of  a  central  gear  meshing  with  pinions  on  each 
of  the  spindles.  Feed  motion  is  furnished  by  a  barrel  cam, 
which  provides  for  raising  or  lowering  the  spider  that  carries 
the  drills.  Indexing  is  accomplished  by  rotating  the  turret 


MULTIPLE-SPINDLE  DRILLING  MACHINES  55 

that  carries  the  work-spindles;  and  the  release  of  the  locking 
bolt  that  secures  this  turret  in  place,  during  the  performance  of 
each  drilling  operation,  is  accomplished  by  means  of  an  edge 
cam  carried  at  the  bottom  of  the  feed  cam. 

Five-spindle  Machine  with  Indexing  Fixture.  —  In  the  opera- 
tion of  multiple-spindle  drilling  machines,  where  it  is  necessary 


Fig.  21.    Special  Drilling  Machine  built  for  Drilling  Bolt  Holes  and 
an  Oil-hole  in  Connecting-rods 

to  perform  a  sequence  of  operations  in  order  to  complete  a  piece 
of  work,  the  development  of  means  for  attaining  the  highest 
rate  of  production  from  the  machines  involves  taking  into 
account  the  relative  time  required  for  the  performance  of  the 
different  operations  necessary  to  complete  drilling  the  work. 
For  instance,  if  the  piece  to  be  machined  has  one  short  hole 

4G 


56  MODERN  DRILLING  PRACTICE 

which  can  be  rapidly  completed  and  one  deep  hole  which  takes 
more  time  to  drill,  due  consideration  must  often  be  paid  to  that 
fact  in  laying  out  the  method  of  handling  the  work.  If  this  is 
not  done,  the  machine  engaged  in  drilling  the  shallow  hole  will 
be  idle  for  a  substantial  portion  of  the  day,  and  hence  will  be 
earning  only  a  part  of  the  possible  return  on  the  money  invested 
in  it.  An  example  of  how  provision  has  been  made  for  taking 
care  of  a  set  of  operations  which  vary  considerably  in  length  is 
shown  in  Fig.  21,  which  illustrates  a  special  Foote-Burt  multiple- 
spindle  drilling  machine  built  for  the  Willys-Overland  Co.  for 
use  in  drilling  two  bolt  holes  and  an  oil-hole  in  the  large  end  of 
the  connecting-rods.  To  arrange  the  work  so  that  the  time 
required  for  drilling  the  two  deep  bolt  holes  will  not  represent 
the  limiting  condition,  the  machine  was  designed  with  five 
spindles  and  an  indexing  work-holding  fixture. 

A  connecting-rod  forging  is  put  in  place  at  the  loading  station, 
after  which  the  fixture  is  indexed  to  bring  this  piece  under  the  first 
pair  of  drilling  spindles.  These  spindles  cut  half  way  through 
the  bolt  holes,  after  which  the  work  is  indexed  to  a  second 
pair  of  spindles  which  complete  drilling  these  holes.  The  work 
is  then  indexed  once  more  to  bring  it  under  a  single  spindle 
which  drills  the  oil-hole,  and  the  fourth  indexing  brings  it  back 
to  the  loading  station,  where  the  drilled  piece  is  removed  and  a 
fresh  forging  substituted.  For  each  indexing  movement  one 
finished  piece  is  drilled,  and  by  dividing  the  drilling  of  the  deep 
bolt  holes  between  two  pairs  of  spindles,  a  balance  is  secured 
between  the  time  involved  in  drilling  these  holes  and  that  re- 
quired for  drilling  the  oil-hole,  so  that  none  of  the  spindles  on 
the  machine  is  kept  idle  for  a  substantial  length  of  time.  The 
work  is  located  on  this  fixture  by  pilots  fitting  into  the  two 
bearing  holes  that  were  drilled  by  a  preceding  operation,  and  a 
C-washer  at  the  upper  end  secures  the  work  without  making  it 
necessary  to  do  more  than  loosen  the  bolt  sufficiently  to  slip  this 
washer  out  so  that  the  work  may  be  lifted  over  the  nut.  The 
material  consists  of  drop-forgings  and  the  connecting-rods  are 
drilled  at  the  rate  of  720  per  eight-hour  day  from  each  machine. 
The  two  bolt  holes  are  ff  inch  in  diameter  by  iyj  inch  deep, 


MULTIPLE-SPINDLE  DRILLING  MACHINES  57 

and  the  oil-hole,  which  is  for  a  J-inch  pipe  tap,  is  f  f  inch  in  diam- 
eter by  -£Q  inch  deep.  The  drilling  operation  is  performed  at  a 
speed  of  325  revolutions  per  minute  with  a  feed  of  0.005  mc^  Per 
revolution.  The  slow  speed  at  which  this  operation  is  performed 
is  due  to  the  fact  that  it  is  necessary  to  hold  the  distance 
between  each  bolt  hole  center  and  a  corresponding  milled  sur- 
face on  the  connecting-rod,  and  if  the  drills  are  forced,  there 
will  be  danger  of  their  "  running  out." 

Auxiliary  Multiple  Drilling  Heads  and  Drill  Speeders.— 
There  should  be  a  clear  understanding  of  the  difference  be- 
tween the  terms  "  auxiliary  multiple  drilling  head  "  and  "  drill 
speeder."  The  former  type  of  equipment  is  used  in  connection 
with  a  single-spindle  drilling  machine  to  provide  for  simul- 
taneously drilling  a  number  of  holes,  and  the  latter  is  employed 
for  speeding  up  a  small  drill  which  is  used  for  drilling  oil-holes 
or  small  tap-holes  in  large  castings  that  are  being  handled  under 
a  heavy  drilling  machine.  The  use  of  such  a  machine  is  neces- 
sary for  drilling  the  large  holes  and  also  to  provide  for  reaching 
these  small  holes  in  large  pieces  of  work.  As  the  spindle  speeds 
provided  on  high-duty  drilling  machines  are  too  slow  for  the 
efficient  operation  of  small  drills  used  for  drilling  tap-holes, 
oil-holes,  etc.,  it  is  necessary  to  provide  for  the  performance  of 
such  operations  by  making  use  of  a  drill  speeder,  which  is  simply 
an  auxiliary  drill  head  mounted  on  the  drilling  machine  spindle 
and  provided  with  gearing  that  gives  the  increase  of  speed 
necessary  for  driving  small  drills  at  the  proper  number  of  revolu- 
tions per  minute. 

As  compared  with  these  conditions,  auxiliary  multiple  drill- 
ing heads  may  be  provided  with  the  necessary  arrangement 
of  gearing  to  increase  the  speed  of  the  drills,  to  drive  these 
drills  at  the  same  speed  as  the  machine  spindle,  or  to  make  a 
variation  in  the  speeds  of  different  sizes  of  drills  carried  in  the 
head.  The  arrangement  of  gearing  in  any  drilling  head  will 
depend  entirely  upon  the  particular  conditions  which  must  be 
met.  The  spindles  of  auxiliary  multiple  drilling  heads  used  on 
sensitive  high-speed  machines  usually  run  at  the  same  speed  as 
the  drilling  machine  spindle. 


MODERN  DRILLING  PRACTICE 


Application  of  Multiple  Drilling  Heads.  —  The  following  in- 
stance is,  perhaps,  typical  of  the  classes  of  work  for  which  auxil- 
iary multiple  drilling  heads  are  employed. 

A  certain  firm  engaged  in  machining  clutch  rings  for  several 
different  automobile  manufacturers  often  has  orders  for  sev- 
eral thousand  of  each  kind  of  ring,  but  it  may  only  be  possible 


Fig.  22.    Four-spindle  Auxiliary  Drill  Head  for  Machining  Motor 
Cylinder  Blocks 

to  obtain  a  few  thousand  drop-forgings  for  these  rings  at  one 
time.  Experience  has  shown  that  it  is  economical  to  employ 
single-spindle  drilling  machines  equipped  with  auxiliary  multi- 
ple heads  for  each  different  type  of  ring  to  be  drilled.  These 
heads  can  be  readily  interchanged  to  adapt  the  same  machines 
for  drilling  different  types  of  rings.  The  increased  production 
possible  with  machines  equipped  in  this  way,  as  compared 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


59 


with  the  use  of  single-spindle  machines,  will  be  readily  under- 
stood when  it  is  learned  that  the  production  was  increased 
from  290  rings  per  day  for  one  man  on  a  single-spindle  drilling 
machine  to  2700  rings  per  day  from  a  machine  equipped  with 
an  auxiliary  multiple  head.  The  preceding  instance  is  typical 
of  the  use  which  is  made  of  auxiliary  multiple  heads;  namely, 
to  enable  a  single-spindle  drilling  machine 
of  moderate  cost  to  drill  several  holes  sim- 
ultaneously. In  cases  where  holes  of  dif- 
ferent sizes  have  to  be  drilled  at  the  same 
setting,  it  is  necessary  to  have  special 
gearing  to  provide  for  driving  different 
drills  at  the  proper  cutting  speeds.  Fig. 
22  shows  a  four-spindle  drilling  head  built 
by  the  Sellew  Machine  Tool  Co.,  which 
is  used  in  the  plant  of  the  Peerless  Motor 
Car  Co.  for  machining  motor  cylinder 
blocks.  In  tliis  case,  the  drilling  machine 
is  rather  heavy  and  the  head  is  of  corre- 
spondingly rugged  construction. 


Fig.  23  shows  an  eighteen-spindle  auxil-  Fte-  23-    Eighteen-spin- 

dle  Auxiliary  Drill  Head 

iary  head  that  was  designed  and  built 
by  the  Langelier  Mfg.  Co.,  for  drilling  and  countersinking 
in  multiples  the  ninety-five  holes  of  the  center  group  in 
the  radiator  support  shown  in  Fig.  24.  The  illustration 
shows  a  cold-rolled  steel  plate  f  inch  thick  by  2T9g-  inches 
wide  and  22^  inches  long.  The  six  end  holes  in  the  plate  are 
punched  and  the  Jf -inch  holes  are  drilled  and  countersunk  with 
the  multiple  head.  Fig.  24  also  shows  the  arrangement  of  the 
spindles  in  the  drilling  head.  These  spindles  are  located  to 
correspond  with  every  other  hole  in  the  plate  in  a  group  of 
thirty  holes;  this  staggering  of  the  spindles  was  necessary  in 
order  to  obtain  a  strong  spindle  construction.  Each  group  of 
thirty  holes  in  the  plate  is  drilled  and  countersunk  in  two  opera- 
tions. The  plate  has  ninety-five  holes  and  the  attachment  drills 
them  in  groups  of  thirty  holes,  two  operations  being  required 
to  drill  each  group.  There  are  three  groups,  and  the  remaining 


6o 


MODERN  DRILLING  PRACTICE 


cross-row  of  five  holes  has  to  be  drilled  singly.  Eighteen  holes 
can  be  drilled  and  countersunk  in  five  seconds.  The  plate  is 
held  and  moved  to  its  different  drilling  positions  by  an  indexing 
fixture  that  is  fastened  to  the  table  of  the  drilling  machine. 
The  lengthwise  movement  of  the  fixture  corresponds  to  the 
shift  between  groups  and  the  crosswise  index  to  the  |-inch 
movement  required  for  the  two  operations  in  each  group.  For 
each  of  the  two  operations  on  a  group  of  thirty  holes,  fifteen 
of  the  eighteen  spindles  in  the  head  are  in  operation  and  the 


LAY-OUT  OF  SPINDLES  IN  DRILL  HEAD 


Machinery 


Fig.  24.  Radiator  Support  in  which  Holes  are  drilled  with  Head 
shown  in  Fig.  23  by  traversing  Work  Sidewise  and  Length- 
wise between  Successive  Operations.  Below  is  shown  Lay- 
out of  Spindles  in  Drill  Head 

drills  carried  by  the  other  three  spindles  hang  over  the  side 
of  the  work. 

The  tools  used  are  a  combined  drill  and  countersink.  The 
shanks  are  squared  and  fit  into  a  square  socket  in  the  spindle 
collets.  Adjustment  of  the  tools  for  producing  uniform  coun- 
tersinking is  obtained  by  an  adjusting  screw  that  is  tapped 
into  the  squared  end  of  the  tool  and  butts  against  the  bottom 
of  the  square  socket  in  the  collet.  This  requires  the  tool  to  be 
taken  out  and  may  seem  a  slow  method  of  adjustment,  but  it 
has  been  proved  that,  after  they  have  once  been  adjusted,  it  is 


MULTIPLE-SPINDLE  DRILLING  MACHINES 


6l 


a  simple  matter  to  keep  them  so.  The  ends  of  the  collets  are 
taper  threaded  and  split,  and  the  tools  are  held  in  the  collets  by 
pinch  nuts.  The  pinch  nuts  are  tightened  or  loosened  by  a 
sleeve  T-wrench  which  telescopes  the  tools.  The  drilling  head 
is  adjustable  rotatively  and 
can  be  set  in  any  position 
in  the  housing  without  af- 
fecting its  running.  The 
housing  is  attached  to  the 
feed  sleeve  of  the  drill  press 
by  a  clamp  nut. 

Indexing  Multiple  Drill- 
ing Machine.  —  In  a  cer- 
tain type  of  intercooler 
tube  plate,  it  is  required 
to  drill  eighty-four  f-inch 
holes,  and  as  the  plates  in 
which  these  holes  must  be 
drilled  are  only  4!  inches 
in  diameter  by  f  inch 
thick,  it 
that  the 

holes  is  too  close  to  make 
it  possible  for  the  work  to 
be  done  on  any  standard 
type  of  multiple-spindle 
drilling  machine.  Fig.  25 
shows  a  special  multiple- 
head  machine  built  by  the 
Langelier  Mfg.  Co.,  which 
is  equipped  with  an  index- 
ing work-holding  fixture; 
the  multiple  head  of  this  drilling  machine  has  fourteen  spindles, 
and,  by  indexing  the  work  six  times,  provision  is  made  for 
drilling  all  of  the  eighty-four  holes  without  loss  of  time  in 
removing  and  resetting  the  work  or  without  the  necessity  of 
spending  time  in  laying  out  the  holes  and  drilling  them  in  a 


will   be   evident 
spacing    of   the 


Fig.  25.  Multiple  Drilling  Machine  with 
Indexing  Fixture  to  Locate  Work  for 
Six  Successive  Operations  required  to 
drill  Eighty-four  Holes,  as  shown  in 
Fig.  26 


62 


MODERN  DRILLING  PRACTICE 


single-spindle  machine.  Fig.  26  shows  at  Ay  B,  C,  Z>,  and  £, 
respectively,  the  condition  of  the  work  after  the  first,  second, 
third,  fifth,  and  sixth  drilling  operations.  The  piece  of  work 
after  the  fourth  operation  has  been  performed  on  it  is  not 
shown  in  this  illustration.  The  distance  between  holes  in 
the  finished  sheet  is  only  ij  times  the  drill  diameter,  which 
shows  how  closely  the  drills  have  to  be  spaced.  For  hold- 
ing and  locating  the  work,  the  machine  is  provided  with 


Fig.  26.  Condition  of  Work  done  on  Machine  shown  in  Fig.  25, 
after  First,  Second,  Third,  Fifth,  and  Sixth  Drilling  Opera- 
tions have  been  performed 

a  three-jawed  indexing  fixture  mounted  on  the  table  of  the 
machine,  and  this  fixture  is  laid  out  so  that  the  work  of  index- 
ing one-sixth,  revolution  between  each  of  the  six  successive 
operations  may  be  accomplished  rapidly.  A  machine  of  this 
kind  could  be  built  with  a  suitable  drill  head  and  work-holding 
fixture  to  provide  for  drilling  other  pieces  where  the  spacing 
of  the  holes  is  too  close  to  make  it  possible  for  the  work  to  be 
done  economically  on  machines  of  standard  design. 


CHAPTER   III 

AUTOMATICALLY   CONTROLLED   DRILLING   MACHINES 
OF   SPECIAL   DESIGN 

THERE  are  many  classes  of  work  where  semi-automatic  or 
fully  automatic  drilling  machines  may  be  used  to  extremely 
good  advantage.  As  a  general  proposition,  the  work  adapted 
for  being  drilled  on  machines  of  this  class  is  of  relatively  small 
size,  although  this  is  not  necessarily  the  case.  With  automati- 
cally controlled  drilling  machines,  the  high  production  secured 
is  largely  due  to  the  possibility  of  effecting  a  great  reduction  in 
the  idle  time  of  the  machine,  as  a  result  of  means  provided  for 
continuous  operation  of  the  drilling  machine  spindle  or  spindles, 
and  the  possibility  of  having  the  operator  constantly  employed 
in  removing  drilled  pieces  from  the  work-holding  fixture  and 
substituting  fresh  blanks. 

Five-spindle  Semi-automatic  Machine.  —  Fig.  i  shows  a 
five-spindle  semi-automatic  drilling  machine  built  by  the  De- 
troit Tool  Co.  The  machine  shown  is  used  in  the  factory  of  the 
Willys-Overland  Co.  Two  spindles  are  engaged  in  drilling  a 
cross-hole  in  hood  catch  stems,  while  the  other  three  spindles 
on  the  machine  are  employed  for  drilling  a  longitudinal  hole 
in  the  end  of  torsion  yoke  pivot  pins.  In  each  case,  the  work  is 
secured  in  a  cam-operated  V-block  fixture  which  is  tightened  or 
loosened  by  a  single  movement  of  the  binding  lever.  The  five 
spindles  on  this  machine  are  controlled  by  a  cam-actuated  feed 
mechanism  arranged  in  such  a  way  that  the  spindles  are  ad- 
vanced to  the  work  in  consecutive  order.  This  makes  it  pos- 
sible for  the  operator  to  be  constantly  employed  removing 
drilled  pieces  and  substituting  blanks  in  the  work-holding 
fixtures,  and  by  the  time  he  has  reached  the  fixture  at  the  right- 
hand  end  of  the  machine,  the  piece  in  the  fixture  at  the  extreme 
left  has  been  drilled  and  the  spindle  withdrawn;  consequently 

63 


64  MODERN   DRILLING   PRACTICE 

the  operator  can  start  right  in  again  removing  drilled  pieces 
and  substituting  blanks,  this  order  being  kept  up  continually. 
On  the  hood  catch  stem  the  cross-hole  is  drilled  with  a  No.  21 
drill  (0.159  incn  m  diameter)  and  the  hole  is  H  inch  deep.  The 
drills  are  operated  at  990  revolutions  per  minute  with  a  feed  of 
0.002  inch  per  revolution;  the  use  of  this  low  speed  is  necessary 
on  account  of  the  larger  sized  drills  used  in  the  other  three 
spindles  of  the  machine.  The  production  is  3600  pieces  in  an 
eight-hour  working  day.  In  drilling  the  longitudinal  hole  in  the 
torsion  yoke  pivot  pin,  the  hole  is  drilled  to  receive  a  f -inch  tap 


Fig.  i.     Five-spindle  Semi-automatic  Drilling  Machine 

and  is  T9g  inch  in  depth.  The  machine  is  operated  at  the  same 
speed  and  feed  employed  for  the  previous  operation,  although 
the  feed  is  really  too  light  for  this  size  of  drill.  The  production 
is  3600  pieces  per  eight-hour  working  day. 

Fixture  for  Increasing  Feed  Range.  —  While  the  five-spindle 
semi-automatic  drilling  machine  is  shown  in  Fig.  i  engaged  in 
the  performance  of  drilling  operations  on  two  classes  of  pins, 
it  must  not  be  inferred  that  the  scope  of  this  machine  is  in 
any  way  restricted  to  the  drilling  of  cylindrical  shaped  pieces. 
Where  suitable  work-holding  fixtures  are  made,  this  machine  is 
adapted  for  drilling  pieces  of  a  great  variety  of  shapes  and 
sizes,  and  in  all  cases  advantage  is  taken  of  the  ability  of  keep- 
ing the  operator  constantly  employed  in  loading  work  into  the 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       65 


fixtures  while  drilling  operations  are  being  performed  on  pieces 
held  in  other  fixtures. 

Where  the  pieces  to  be  drilled  are  of  such  a  character  that 
the  depth  of  hole  required  is  in  excess  of  the  maximum  feed 
movement  provided  by  the  throw  of  the  cam,  provision  for 
drilling  such  pieces  may  be  made  by  designing  a  special  work- 
holding  fixture  of  the  general  type  shown  in  Fig.  2.  This  partic- 
ular fixture  was  designed  for  drilling  staybolts  which  are  held  in 
jaws  A ,  these  jaws  being  quickly  opened  or  closed  by  means  of 
lever  B.  The  body  of  the  fixture  on  which  the  work  is  sup- 
ported is  carried  by  a  slide  C,  and  provision  is  made  for  travers- 


Machinery 


Fig.  2.     Fixture  for  Use  in  Drilling  Holes  on  Machine  shown 
in  Fig.  i 

ing  this  slide  in  a  direction  opposite  to  the  feed  movement  of  the 
drilling  machine  spindle  by  means  of  hand-lever  D.  In  operat- 
ing a  drilling  machine  equipped  with  a  fixture  of  this  kind,  the 
work  is  first  held  in  the  fixture  with  slide  C  in  its  position  farthest 
away  from  the  drilling  machine  spindle,  and  in  this  position  the 
drill  is  fed  into  the  work.  After  the  hole  has  been  drilled  to  the 
full  depth  in  this  position  and  the  drill  has  been  backed  out  of 
the  work,  slide  C  is  advanced  by  manipulating  hand-lever  D 
and  the  fixture  is  secured  in  the  forward  position.  Then  the 
next  time  the  spindle  is  fed  forward  by  the  cam,  the  drill  com- 
pletes cutting  the  hole  to  the  required  depth.  Suitable  fixtures 


66  MODERN  DRILLING  PRACTICE 

of  this  kind  can  be  designed  to  meet  the  requirements  of  a 

variety  of  classes  of  work  where  deep  holes  have  to  be  drilled. 

Six-spindle  Semi-automatic  Machine.  —  A  somewhat  similar 

type  of  semi-automatic  drilling  machine  to  the  one  previously 


Fig.  3.  Six-spindle  Semi-automatic  Drilling  Machine  with  Double 
Work-holding  Fixture  which  provides  for  Loading  Six  Sections 
of  Fixture  while  Work  is  being  drilled  in  Other  Six  Positions 

described  is  shown  in  Fig.  3,  this  machine  being  built  by  the 
National  Acme  Co.  It  will  be  seen  that  this  is  a  six-spindle 
machine,  and  while  in  general  appearance  it  resembles  the  one 
shown  in  the  preceding  illustration,  the  method  of  operation 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       67 

differs  considerably.  On  this  machine,  all  of  the  spindles  feed 
forward  simultaneously,  and  to  provide  for  reducing  the  idle 
time  of  both  the  machine  and  operator,  the  work-holding  fixture 
is  designed  to  carry  twelve  pieces.  This  fixture  is  arranged  in 
such  a  way  that  while  six  pieces  of  work  are  being  drilled,  fin- 
ished parts  may  be  removed  from  the  other  six  work-holding 
fixtures  and  fresh  blanks  substituted.  When  the  drilling  opera- 
tion has  been  completed  and  the  drills  have  been  automatically 
withdrawn  from  the  work,  the  operator  rocks  the  work-holding 
fixture  over  on  its  oscillating  support  so  that  the  fresh  blanks 
are  brought  into  the  drilling  position.  He  can  then  remove  the 
drilled  pieces  and  substitute  blanks  in  the  manner  previously 
described.  Some  remarkably  high  rates  of  production  are 
secured  on  these  machines.  For  instance,  at  the  plant  of  the 
Ford  Motor  Co.  machines  of  this  type  are  employed  for  drilling 
cross-holes  in  bolts  of  the  form  shown  below  the  machine  in 
Fig.  3.  In  drilling  a  |-inch  hole  through  a  f-inch  bolt  body, 
the  machines  are  operated  at  1500  revolutions  per  minute  and 
the  rate  of  production  is  10,000  bolts  per  eight-hour  working 
day.  Another  job  performed  on  this  machine  consists  of  drill- 
ing a  J-inch  hole,  y9g  inch  deep,  through  the  head  of  a  bolt. 
Running  the  spindles  at  the  same  speed,  the  production  is  6000 
bolts  per  eight-hour  day. 

Semi-automatic  Drilling  Machine  with  Indexing  Fixture. — 
In  the  two  preceding  types  of  drilling  machines  the  spindles 
are  advanced  and  withdrawn  automatically,  but  the  operator 
is  required  to  manipulate  the  work-holding  fixJU'fe  by  hand. 
In  Figs.  4  and  5  there  are  shown  two  machines  built  by  Baker 
Bros.,  which  are  equipped  with  an  automatic  indexing  fixture. 
Near  the  top  of  the  machine  there  is  a  cam-drum  on  which  cams 
are  mounted  to  provide  for  automatically  feeding  the  drills  into 
the  work  and  withdrawing  them,  the  amount  of  feed  motion 
being  regulated  by  the  cams  according  to  the  work  on  which 
the  machine  is  engaged.  Extending  down  from  this  feed  drum 
on  the  left-hand  side  of  the  machine,  there  will  be  seen  a  shaft 
which  is  driven  by  a  pair  of  spur  gears.  This  shaft  transmits 
motion  to  an  indexing  mechanism  located  beneath  the  table  and 


68  MODERN  DRILLING  PRACTICE 

work-holding  fixture,  and  by  this  means  provision  is  made  for 
continuously  indexing  the  work-holding  fixture  to  bring  a  fresh 
blank  or  blanks  into  the  operating  position  to  be  drilled  during 
the  time  that  the  drills  are  being  raised  ready  to  start  the  next 
downward  stroke.  With  an  equipment  of  this  kind  it  is  merely 


Fig.  4.     Semi-automatic  Drilling  Machine  with  Station-type  Work- 
holding  Fixture  which  is  automatically  indexed 

necessary  for  the  operator  to  stand  at  the  front  of  the  machine  so 
that  he  can  remove  finished  pieces  and  substitute  fresh  blanks 
to  be  drilled. 

Fig.  4  shows  a  machine  engaged  in  drilling  external  brake- 
band anchors  in  the  plant  of  the  Willys-Overland  Co.  The 
operation  consists  of  drilling  eight  Jf-inch  holes,  which  are 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       69 


approximately  T3g  inch  in  depth.  Four  holes  are  drilled  at  one 
end,  after  which  the  piece  is  reversed  end  for  end  in  the  fixture, 
to  provide  for  drilling  the  other  four  holes.  In  each  case  the  work 
is  located  in  the  fixture  by  a  pilot  that  enters  the  large  central 
hole,  but  alternate  stations  on  the  fixture  are  designed  to  locate 


Fig.  5.    Semi-automatic  Drilling  Machine  drilling  Holes  in  Ends 
of  Levers 

the  work  by  different  methods,  according  to  whether  the  first 
four  holes  have  or  have  not  already  been  drilled.  When  the 
piece  is  first  set  up  in  the  fixture,  it  is  slipped  over  the  pilot, 
entering  the  center  hole,  after  which  the  lever  A  is  turned  to 
operate  an  "  equalizer  "  that  lines  up  the  work  properly;  then 
wing-nut  B  is  tightened,  which  results  in  raising  a  clamping 


70  MODERN  DRILLING  PRACTICE 

lever  that  secures  the  work  in  place  on  the  under  side  of  the 
jig-plate  that  forms  the  top  of  the  work-holding  fixture.  In 
this  position  the  first  four  holes  are  drilled,  and  when  the  piece 
has  again  come  around  to  the  front  of  the  fixture,  the  operator 
releases  the  clamps,  and  after  taking  this  piece  out  of  the  fixture, 
sets  it  up  again  in  a  work-holding  fixture  located  on  the  next 
station.  In  this  position,  the  work  is  located  by  a  pilot  entering 
the  large  center  hole  and  by  a  small  pin  that  enters  one  of  the 
holes  which  have  just  been  drilled.  Then,  by  tightening  the 
wing-nut  Z>,  the  piece  is  clamped  in  place.  At  each  downward 
movement  of  the  spindle  of  the  drilling  machine  eight  holes  are 
drilled  —  four  in  a  piece  which  has  already  had  the  first  four 
holes  drilled  and  four  in  a  fresh  blank  —  so  that  one  drilled 
piece  is  obtained  for  each  traverse  of  the  spindle.  From  this  it 
will  be  apparent  that  the  index  mechanism  is  arranged  so  that 
the  work-holding  fixture  is  indexed  through  two  stations  on 
the  fixture  each  time  that  the  spindle  of  the  drilling  machine  is 
raised.  The  machine  is  operated  at  such  a  speed  that  the  drills 
run  at  1 100  revolutions  per  minute,  with  a  feed  of  0.002  inch  per 
revolution;  and  operating  under  these  conditions,  576  pieces  are 
drilled  in  an  eight-hour  working  day.  The  material  is  malleable 
iron. 

Fig.  5  shows  another  application  of  the  Baker  Bros,  semi- 
automatic drilling  machines  in  the  plant  of  the  Willys-Overland 
Co.  This  illustration  shows  the  operation  of  drilling  two  holes 
f  inch  in  diameter  by  0.372  inch  deep,  and  one  hole  ff  inch  in 
diameter  by  1.120  inch  deep,  respectively,  in  the  rear  axle 
external  brake-band  lever.  The  material  is  malleable  iron  and 
the  operation  is  performed  at  a  speed  of  650  revolutions  per 
minute,  with  a  feed  of  0.003  inc^  Per  revolution.  The  produc- 
tion is  600  pieces  per  eight-hour  working  day.  The  drilling 
machine  is  equipped  with  a  four-spindle  auxiliary  head,  but  only 
three  of  the  spindles  are  provided  with  twist  drills.  This  is  not 
due  to  the  fact  that  use  is  being  made  of  a  four-spindle  head  that 
happened  to  be  available,  but  because  of  the  necessity  for  drill- 
ing both  right-  and  left-hand  brake-band  levers.  In  drilling 
levers  of  the  opposite  hand,  the  drill  shown  in  the  right-hand 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       71 


spindle  is  removed  and  set  up  on  the  spindle  at  the  left  hand 
of  the  central  position.  In  the  work-holding  fixture  used  on 
this  machine,  the  end  of  the  work  is  located  by  means  of  a  V- 
block,  and  clamping  is  effected  by  means  of  wing-nuts  A  which 
bind  the  outer  V-block  against  the  end  of  the  work.  Supporting 
pads  on  the  fixture  prevent  the  work  from  springing. 


Fig.  6.    Semi-automatic  Continuous-feed  Drilling  Machine  equipped 
for  Drilling  Cotter-pin  Holes 

Cotter-pin  Hole  Drilling  Machine.  —  Fig.  6  shows  a  machine 
known  as  the  No.  i  semi-automatic  continuous-feed  drilling 
machine,  which  is  built  by  the  Langelier  Mfg.  Co.  This  ma- 
chine is  particularly  adapted  for  drilling  small  holes,  such  as 
cotter-pin  holes  in  long  pins,  balls,  screws,  nuts,  and  work  of  a 
similar  nature.  It  is  built  for  various  sizes  of  work,  with  any 
number  of  drilling  heads  up  to  and  including  ten.  In  the  illus- 
tration, eight  heads  are  shown,  each  head  having  two  drilling 


72  MODERN  DRILLING  PRACTICE 

spindles,  located  one  above  the  other,  making  a  total  of  sixteen 
drilling  spindles.  The  piece  drilled  was  a  pin  f  inch  in  diameter, 
having  two  f-inch  cotter-pin  holes  crosswise  through  the  ends, 
the  distance  between  the  holes  being  ifj  inch.  The  drilling 
spindles  feed  outward  as  they  travel  around  the  center  of  the 
machine,  the  two  spindles  in  each  head  drilling  the  two  holes 
in  the  pins  at  the  same  time.  Each  of  the  drilling  heads  has  a 
vise  which  opens  and  closes  automatically  as  it  passes  the  opera- 
tor, or  may  be  closed  by  the  operator  with  a  foot-pedal  the 
instant  he  puts  the  work  in  the  vise.  Seven  of  the  drilling 
heads  are  drilling  continuously,  while  the  eighth  one  is  in  the 
loading  position,  where  the  operator  removes  the  finished  piece 
and  replaces  a  blank  which  is  to  be  drilled.  The  drill  is  with- 
drawn as  it  passes  the  loading  position  and  the  corresponding 
vise  opens  automatically  for  the  operator  to  remove  the  work 
and  replace  it  with  a  blank.  The  operator  can  either  sit  or 
stand,  as  desired,  while  inserting  fresh  blanks  in  the  vises.  The 
vises  are  closed  either  automatically  or  by  means  of  a  foot-treadle. 
All  that  the  operator  has  to  do  is  to  remove  the  finished 
pieces  and  insert  blanks  in  the  vises,  which  can  be  made  to 
hold  pieces  of  various  sizes  and  shapes.  Either  vertical  or 
horizontal  vises  may  be  used,  the  style  being  determined  by 
the  class  of  work  upon  which  the  machine  is  to  operate.  When 
long  pieces  are  to  be  drilled,  the  vises  are  made  to  hold  the 
work  in  a  vertical  position,  the  work  extending  up  any  reason- 
able length  that  can  be  operated  upon.  On  some  classes  of 
work  an  automatic  ejecting  device  can  be  used  to  advantage, 
so  that,  when  the  jaws  open  automatically,  the  work  will  be 
forced  out.  With  a  machine  equipped  in  this  way,  all  that 
the  operator  has  to  do  is  to  place  fresh  blanks  in  the  vises. 
The  maximum  feed  travel  is  ij  inch,  and  the  chucks  will  take 
drills  up  to  J  inch  in  diameter.  The  feed-cam  that  operates 
the  spindles  is  easily  removed,  so  that  cams  to  give  different 
ranges  may  readily  be  substituted.  When  deep  holes  are  to  be 
drilled,  the  cams  are  made  to  withdraw  the  drills  frequently, 
thus  breaking  and  clearing  the  chips  from  the  holes.  The  feed 
of  the  drills  can  be  changed  to  suit  the  depth  of  holes  and  the 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       73 

sizes  of  drills.  Provision  is  made  for  ample  lubrication  of  the 
drills,  the  lubricant  being  forced  between  the  vise  jaws  and  the 
work,  thus  keeping  the  work  flooded  at  the  point  of  drilling  so 
that  the  highest  possible  feed  and  cutting  speed  may  be  em- 
ployed. A  circular  pan  surrounds  the  drilling  heads,  and  holds 
the  drilled  work  and  chips.  The  oil  flows  into  the  base,  and  is 
pumped  back  to  the  work  by  a  circulating  pump. 

An  idea  of  the  productive  capacity  of  the  machine  will  be 
obtained  from  the  following  example:  Automobile  chain  pins 
J  inch  in  diameter  are  drilled  with  o.i2i-inch  drills  running  at 
2 200  revolutions  per  minute,  the  production  being  12,000  pins 
per  ten-hour  day.  The  capacity  of  the  machine  for  round 
pieces  with  two  sets  of  vise  jaws  is  from  J  to  i  inch,  the  first  set 
taking  from  J  to  f  inch  and  the  second  set  from  f  to  i  inch. 
The  jaws  carry  a  drill  guide  bushing  which  centers  the  drill 
accurately.  These  jaws  can  be  quickly  changed  when  it  is 
required  to  operate  the  machine  on  some  other  class  of  work. 

Six-head  Continuous-feed  Drilling  Machine.  —  Fig.  7  shows 
a  six-head  continuous-feed  multiple  drilling  machine  with  which 
parts  containing  practically  any  number  of  holes  may  be  drilled 
continuously,  without  any  loss  of  time  for  the  ejection  of  drilled 
pieces  or  inserting  blank  ones.  This  drilling  machine  is  built  by 
the  Langelier  Mfg.  Co.  The  rate  of  production  attained  with 
this  machine  will  be  readily  grasped  upon  noting  that  the  work 
was  drilled  by  an  average  unskilled  operator  at  the  rate  of 
fourteen  completely  drilled  pieces  per  minute,  or  a  total  of 
8400  pieces  or  42,000  holes  in  ten  hours.  The  work  is  a  forging 
y3g  inch  thick,  and  there  are  two  holes  0.199,  two  holes  0.261, 
and  one  hole  0.098  inch  in  diameter.  The  speeds  for  these  three 
sizes  of  drills  are  585,  455,  and  1200  revolutions  per  minute, 
respectively,  with  a  feed  of  0.0018  inch  per  revolution.  If  it  had 
been  necessary  that  the  pieces  be  drilled  with  more  than  five 
holes  each,  the  total  number  of  holes  drilled  in  ten  hours  would 
have  been  still  greater,  because  all  of  the  holes  in  each  piece, 
no  matter  how  great  the  number,  are  drilled  in  practically  the 
same  time  that  it  would  take  to  drill  a  single  hole.  The 
machine  works  on  six  pieces  simultaneously  and  continuously. 


74 


MODERN  DRILLING  PRACTICE 


Each  head  is  fitted  with  a  "  steady  "  jig  for  supporting  and 
accurately  starting  the  drill  ends.    The  jig  is  adjustable  verti- 


Fig.  7.  Multiple-head  Drilling  Machine  which  provides  for  Drill- 
ing Parts  containing  practically  any  Number  of  Holes  without 
Loss  of  Time  for  Ejection  of  Drilled  Pieces  or  Setting  up  Un- 
drilled  Blanks 

cally  to  compensate  for  the  shortening  of  the  drills  by  grind- 
ing, and  is  also  under  spring  tension  so  as  to  exert  pressure 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       7$ 

on  the  work  while  it  is  being  drilled.  The  pieces  to  be  drilled 
are  located  and  held  in  position  by  a  three-point  supporting 
pressure  lever  fixture,  the  fixture  body  being  screwed  to  the 
table  permanently.  Each  type  of  work  has  a  separate  fixture 
seat  of  its  own  that  can  be  quickly  removed  and  replaced. 
The  pieces  to  be  drilled  are  gripped  by  a  short  fulcrumed  lever 
under  spring  tension,  the  longest  end  being  depressed  to  re- 
lease the  work  by  passing  under  a  segment  cam  that  is  located 
directly  in  front  of  the  operator  and  fastened  to  the  rim  of 
the  oil-pan.  The  segment  cam  is  stationary  and  is  adjustable 
vertically  so  as  to  give  just  the  proper  amount  of  opening. 
The  machine  consists  of  a  box  base  having  a  vertical  station- 
ary post  at  the  center,  around  which  revolves  a  member  carry- 
ing the  six  drilling  heads  and  tables  upon  which  the  work- 
holding  fixtures  are  fastened.  Each  drilling  head  with  its 
table  revolves  in  unison.  The  drilling  feed  is  accomplished 
by  the  upward  movement  of  the  tables;  and  at  the  lower  ex- 
tremity of  each  table  slide  there  is  a  roller  having  contact  with 
a  circular  feed-cam  that  is  fastened  to  the  base  of  the  machine. 
The  drilling  is  done  against  the  tension  of  a  spring,  as  a  safe- 
guard against  very  dull  drills  and  incorrect  chucking  of  work 
in  fixtures  by  the  operator.  Tension  springs  pulling  downward 
on  the  tables  insure  them  having  contact  with  the  feeding  edge 
of  the  cam  at  all  times,  especially  on  the  return. 

The  revolving  member  carrying  the  drilling  heads  and  tables 
is  actuated  by  a  Hindley  worm  and  gear  located  inside  of  the 
central  circular  flange  supporting  the  feed-cam.  The  work 
shaft,  in  turn,  is  belted  to  the  clutch  shaft,  on  one  end  of  which 
is  a  pair  of  miter  gears  that  receive  motion  from  the  main  driv- 
ing pulley  inside  the  box  base.  The  drilling  heads  are  driven 
by  a  large  central  gear  keyed  to  the  vertical  main  driving  pulley 
shaft  extending  up  through  the  central  post.  The  driven  gears 
on  the  main  spindles  of  the  drilling  heads  are  made  of  com- 
pressed cotton  (Fabroil  gears)  so  as  to  avoid  unnecessary  noise 
and  to  insure  smooth  running.  A  large  stationary  chip-  and 
oil-pan,  supported  by  the  standards,  is  fastened  to  the  base 
that  surrounds  the  machine.  On  the  outer  end  of  the  miter 


76  MODERN  DRILLING  PRACTICE 

gear  shaft  is  mounted  a  Johnson  clutch  that  is  operated  by  a 
foot-lever  which  is  conveniently  located  for  the  operator.  This 
clutch  is  used  to  make  the  circular  feed  of  the  machine  inde- 
pendent of  the  driving  of  the  drilling  heads,  so  that  it  can  be 
instantly  stopped  by  simply  unlocking  the  foot-lever  by  a  side 
thrust  of  the  foot. 

The  cutting  lubricant  is  a  special  mixture  that  is  pumped 
up  through  a  tube  passing  through  the  main  driving  pulley 
shaft  and  then  led  to  each  drilling  head  by  branch  piping.  After 
being  used,  it  flows  to  the  bottom  of  the  circular  oil-pan,  where 
it  is  freed  from  the  chips.  It  then  passes  to  the  top  of  the  base, 
where  it  is  filtered  before  entering  the  reservoir  located  in  the 
bottom  half  of  the  base.  This  machine,  with  slight  modification, 
can  be  used  for  drilling  a  large  variety  of  pieces  having  one  or 
more  holes. 

Semi-automatic  Twelve-spindle  Machine.  —  On  a  machine 
built  by  the  Langelier  Mfg.  Co.  for  drilling  the  brass  stems  of 
pneumatic  tire  valves,  a  shaft  to  which  six  fixtures  are  fastened 
is  mounted  in  a  pan  supported  by  legs  at  a  convenient  height 
for  the  operator.  These  fixtures  are  triangular  in  shape,  having 
their  apexes  flattened  sufficiently  to  receive  split  chucks  for 
holding  the  valve  stems.  These  chucks  are  kept  closed  by 
springs,  and  are  opened  by  small  levers  of  such  shape  that, 
when  the  chucks  are  opened  by  resting  the  palm  of  the  hand  on 
the  levers,  the  work  may  be  inserted  or  removed  by  the  fingers 
of  the  same  hand.  The  machine  is  shown  in  Fig.  8,  and  Fig.  9 
shows  the  work  to  be  drilled.  The  spindles,  which  are  provided 
with  chucks  for  holding  the  drills,  run  in  bushed  bearings  in 
brackets  attached  to  the  outside  of  the  pan,  six  on  the  back 
and  six  in  front,  and  project  through  the  pan  at  an  angle  of  30 
degrees  below  the  horizontal,  thus  being  in  line  with  the  chucks 
that  hold  the  work  in  the  apexes  of  the  triangular  fixtures  on  the 
shaft  above.  There  are  also  two  larger  brackets  attached  to  the 
pan  diagonally  opposite  each  other,  and  extending  out  over 
drums  at  each  end  of  the  machine.  These  brackets  support 
slides  provided  with  rolls  to  engage  with  cam-plates  secured  to 
the  faces  of  the  drums.  Long  bars,  which  are  attached  to  the 


AUTOMATICALLY   CONTROLLED   DRILLING  MACHINES       77 


slides,  extend  through  the  spindle  brackets  and  carry  a  wedge 
for  each  spindle.  When  these  bars  are  drawn  forward  by  the 
revolving  cams  engaging  with  the  rolls  on  the  sides,  the  wedges 
come  in  contact  with  bushings  on  the  spindles,  and  force  the 
drills  inward  toward  the  work.  The  wedge  bars  are  returned  to 


\ 


Fig.  8.  Semi-automatic  Machine  on  which  Provision  is  made  for 
Automatically  Backing  Out  Drill  at  Specified  Intervals  to  Pro- 
vide for  Clearing  Chips  from  Hole 

their  normal  position  by  springs,  and  the  wedges  are  separately 
adjustable,  so  that  the  points  of  the  drills  may  be  kept  in  line. 
The  two  cam-drums  are  driven  by  a  worm  belted  directly 
from  the  countershaft.  At  every  revolution  of  the  cam-drums, 
a  wedge  under  the  rim  of  the  right  drum  withdraws  a  spring 


78 


MODERN   DRILLING   PRACTICE 


lock-pin  from  a  notch  in  the  index  plate  on  the  right  end  of 
the  shaft,  carrying  the  triangular  fixtures,  while  a  toothed 
sector  on  the  left  drum  engages  with  a  pinion  on  the  left  end 
of  the  shaft,  turning  it  one-  third  revolution,  where  it  is  locked 
by  the  pin  springing  into  the  next  notch  in  the  index  plate. 
A  lever  is  provided  for  unlocking  the  fixture  shaft  by  hand, 
and  the  cam-drums  may  be  revolved  by  the  handwheel  on 
the  worm  shaft.  When  the  machine  is  in  operation,  the  pan 
into  which  the  spindles  project  is  filled  with  oil,  so  that  the 
drills  and  work  are  completely  submerged.  The  oil  lubricates 
the  spindles.  A  large  pipe  with  a  stop-cock  is  provided  by 
which  the  oil  may  be  quickly  drawn  off  into  a  pail  placed  on  the 
floor.  The  whole  machine  stands  in  a  large  pan,  which  insures 


Machinery 


Fig.  9.     Type  of  Brass  Pneumatic  Tire  Valve  Stem  drilled  on 
Machine  shown  in  Fig.  8 

cleanliness,  although  the  drills  never  throw  the  oil  and  it  could 
only  be  splashed  out  of  the  upper  pan  by  the  carelessness  of  the 
operator.  The  valve  requires  to  have  a  hole  0.081  inch  in  diam- 
eter drilled  to  a  depth  of  f  inch,  and  then  a  hole  0.0635  iRCh  m 
diameter  is  drilled  \  inch  farther.  The  cam-plates  on  the  faces 
of  the  drums  are  so  made  that  the  drills  are  fed  into  the  work 
about  |  inch,  then  entirely  withdrawn,  and  after  the  oil  has 
cooled,  lubricated,  and  cleared  the  drills  of  chips,  they  are  fed  in 
|  inch  farther,  and  so  on  until  the  required  depth  is  reached. 
The  large  drills  are  in  the  spindles  on  the  back  of  the  machine, 
and  the  small  ones  in  front.  The  triangular  fixtures  run  from 
front  to  back. 

The  operation  of  the  machine  is  as  follows:  A  valve  stem  is 
placed  in  each  of  the  six  chucks  in  the  upturned  apexes  of  the 
fixtures,  then  the  fixture  shaft  is  turned  one-third  revolution 


AUTOMATICALLY   CONTROLLED   DRILLING   MACHINES        79 


toward  the  back,  where  it  is  locked  by  the  spring-pin  in  position 
for  drilling  the  large  holes.  While  the  large  drills  are  operating, 
the  six  chucks,  now  upturned,  are  filled  with  stems,  and  when 
the  large  holes  are  completed  on  the  first  set  of  stems,  the  fix- 
ture shaft  turns  one-third  revolution,  presenting  the  first  set 
of  stems  to  the  small  drills,  the  second  set  to  the  large  drills, 
and  the  third  set  of  chucks  to  the  operator  to  be  filled  with  stems. 


Fig.  10.     Drilling  Machine  with  Four  Sets  of  Three  Opposed 
Spindles  for  Drilling  Twelve  £-inch  Oil-holes 

The  machine  is  now  fairly  under  way,  and  need  not  be  stopped, 
except  for  accident,  until  working  hours  are  over,  as  the  operator 
has  only  to  remove  finished  stems  from  the  chucks,  and  insert 
blanks,  while  the  drills  are  operating  on  the  other  two  sets  of 
stems.  The  drills  make  8000  revolutions  per  minute,  and  at 
this  speed  the  machine  drills  six  valve  stems  every  minute,  or 


8o 


MODERN  DRILLING  PRACTICE 


3600  in  a  day  of  ten  hours.  Although  designed  and  built  for  a 
special  purpose,  this  machine  may  be  adapted  for  a  great  variety 
of  work. 

Motor  Valve  Sleeve  Multiple  Drilling  Machine.  —  For  use  in 
drilling  at  one  operation  the  twelve  f-inch  oil-holes  in  the  outer 
sleeve  of  a  Willys-Overland  motor  valve,  the  Langelier  Mfg.  Co. 
designed  the  multiple  drilling  machine  illustrated  in  Fig.  10. 
A  similar  machine  was  built  for  use  in  drilling  four  J-inch  holes 
in  the  inner  sleeve,  and  the  output  of  each  machine  is  3^  sleeves 
per  minute,  or  2100  per  day.  The  material  is  cast  iron  and  the 


«= =Q3 


MacMnery 


Fig.  ii. 


Close  View  of  Work-holding  Fixture  and  Drilling  Spindles 
of  Machine  shown  in  Fig.  10 


holes  are  approximately  T3g  inch  deep.  The  machines  are  of 
exactly,  the  same  design,  except  that  one  is  equipped  with  twelve 
drill  spindles,  while  the  other  has  only  four  spindles. 

Fig.  ii  shows  a  cross-sectional  view  through  the  drill  jig 
on  the  machine  for  drilling  the  outer  sleeve,  in  which  the  work 
is  shown  in  the  drilling  position.  Referring  to  this  illustration, 
the  method  of  operating  the  machine  will  be  clearly  understood. 
Sleeve  A  is  held  and  located  in  the  drilling  position  by  an  in- 
ternal expanding  arbor  B  mounted  on  tailstock  C}  which  slides 


AUTOMATICALLY  CONTROLLED   DRILLING  MACHINES       8 1 

upon  ways  in  line  with  the  axis  of  the  machine.  Expanding 
arbor  B  is  opened  or  closed  automatically  by  means  of  com- 
pressed air;  the  construction  consists  of  a  split  sleeve  that  is 
attached  directly  to  the  piston  in  the  compressed  air  cylinder; 
and  inside  this  sleeve  there  is  a  fixed  arbor  D  with  a  tapered  end 
that  is  attached  to  the  cylinder  head.  A  slight  travel  of  the 
sleeve  on  this  tapered  portion  of  the  fixed  arbor  causes  the 
sleeve  to  expand  and  hold  the  work  securely,  extra  movement 
being  avoided  by  a  stop  collar  on  the  sleeve  and  tapered  arbor. 

Admission  of  air  to  the  cylinder  is  controlled  by  a  small  piston 
valve  that  is  attached  to  the  tailstock  C  at  the  rear  and  operated 
by  contract  with  a  fixed  stop  attached  to  the  tailstock  slide. 
The  tailstock  is  shown  in  its  outer  or  loading  position  in  Fig.  10, 
movement  of  the  tailstock  slide  being  secured  by  means  of  the 
handwheel  at  the  front  of  the  machine.  The  drilling  position  is 
obtained  by  the  sleeve  to  be  drilled  coming  into  contact  with  a 
stop  E  located  inside  of  drill  jig  F\  this  stop  can  be  adjusted  at 
the  left-hand  end  of  the  machine.  The  tailstock  is  also  auto- 
matically locked  when  in  a  drilling  position,  and  is  unlocked  by 
the  foot- treadle  shown  at  the  front  of  the  bed;  this  lock  is 
adjustable  and  can  be  set  to  suit  the  requirements  of  the  work 
being  drilled. 

Drilling  heads  G  are  located  radially  90  degrees  apart  upon 
a  circular  faceplate  H  that  is  mounted  on  column  /  attached 
to  the  bed  of  the  machine.  Drilling  spindles  K  are  driven  by 
spiral  gears,  the  drives  extending  to  the  rear  and  having  pulleys 
on  their  ends.  The  thrust  is  taken  up  by  ball  thrust  bearings. 
The  feed  of  the  drill  spindles  is  operated  by  a  handwheel  at  the 
right-hand  side  of  the  machine,  which  has  a  spur-gear  connec- 
tion to  a  rim  gear  located  inside  and  concentrically  with  face- 
plate //.  The  rim  gear  carries  a  segment  feed-cam  for  each 
head  that -has  roller  contact  with  the  feed  yoke  of  each  drill 
head.  These  yokes  have  a  clamp  connection  to  the  sleeve  on 
the  outer  end  of  the  drilling  spindles,  and  this  clamp  connection 
provides  ready  means  of  adjusting  the  feeding  position  of  the 
drill  spindles. 


CHAPTER   IV 
SPEEDS   AND    FEEDS   FOR   DRILLING 

THERE  are  so  many  variables  which  enter  into  the  perform- 
ance of  a  drilling  operation  that  it  is  extremely  difficult  to  estab- 
lish anything  in  the  nature  of  hard  and  fast  rules  for  the  speed 
and  feed  that  are  correct  for  drilling  a  hole  of  specified  size  in 
a  given  class  of  material.  It  is  quite  general  practice  for  an 
experienced  mechanic  to  determine  what  appears  to  be  the 
proper  speed  and  feed  for  a  given  job  by  the  use  of  "  cut  and 
try  "  methods.  Experience  will  enable  him  to  tell  very  closely 
what  are  the  proper  conditions  of  operation,  and  with  this  as  a 
basis  he  will  observe  the  operation  of  the  drill,  and  from  that 
judge  whether  he  is  working  under  conditions  that  yield  the 
maximum  production.  The  successful  use  of  high-speed  steel 
drills  often  depends  more  upon  the  conditions  under  which  they 
are  operated  than  upon  the  tools  themselves,  provided  they  are 
properly  made  from  a  suitable  grade  of  steel. 

Advantages  of  Drilling  at  High  Speed.  —  Recent  years  have 
witnessed  great  increases  in  the  speed  at  which  drilling  opera- 
tions are  performed  in  many  shops,  and  the  advocates  of  high- 
speed drilling  —  both  among  builders  of  drilling  machines  and 
users  of  such  equipment  —  claim  that  numerous  advantages 
are  secured  by  drilling  at  these  high  speeds.  There  is  another 
body  of  mechanical  men  who  treat  with  contempt  the  idea  of 
benefits  resulting  from  high-speed  drilling,  and  state  that  this 
is  a  fad  which  has  been  carried  to  great  excess.  In  any  case, 
the  proper  speed  at  which  a  drilling  operation  should  be  per- 
formed is  that  speed  at  which  the  most  desirable  balance  is 
obtained  between  cutting  down  of  production  through  lowering 
the  drilling  speed  and  loss  of  time  through  the  necessity  of  more 
frequently  stopping  the  drilling  machine  to  grind  drills,  where 
higher  drilling  speeds  are  employed.  Owing  to  this  diversity  of 
opinion  in  regard  to  the  most  efficient  speed  at  which  drilling 

82 


SPEEDS  AND   FEEDS  FOR  DRILLING  83 

operations  can  be  performed,  the  following  recommendations 
made  by  different  authorities  should  prove  of  interest  and 
practical  value. 

H.  M.  Norris,  chief  engineer  of  the  Cincinnati-Bickford  Tool 
Co.,  has  made  a  careful  study  of  the  question  of  drilling  speeds, 
and  the  results  of  his  investigations  have  led  him  to  the  con- 
clusion that  occasionally  a  drill  is  found  which  is  capable  of 
standing  up  satisfactorily  at  a  cutting  speed  of  150  feet  per 
minute  in  either  cast  iron  or  steel,  but  it  is  seldom  desirable 
to  drive  anything  but  very  small  drills  at  speeds  in  excess  of 
100  feet  per  minute.  Under  average  conditions  of  operation, 
the  best  results  will  be  obtained  with  a  cutting  speed  of  80  feet 

T  *? 

per  minute  in  cast  iron,  while,  for  steel,  a  speed  of    —  +  76 

feet  per  minute  will  give  satisfactory  results.  Where  this  rule 
is  used,  the  cutting  speed  will  be  decreased  from  100  feet  per 
minute  for  a  ^-inch  drill  to  80  feet  per  minute  for  a  3-inch  drill. 
In  explaining  the  rule,  attention  is  called  to  the  fact  that,  while 
cast  iron  is  cut  dry,  a  lubricant  is  required  for  drilling  steel  and 
a  volume  of  lubricant  sufficient  to  keep  a  ^-inch  drill  cool  at 
100  feet  per  minute  will  only  be  sufficient  to  cool  a  3-inch  drill 
at  80  feet  per  minute. 

Speeds  and  Feeds  Recommended.  —  Selection  of  the  proper 
speed  and  feed  for  a  given  drilling  operation  is  governed  by 
the  diameter  of  the  drill  and  the  kind  of  material  being 
drilled.  Exhaustive  tests  and  close  observation  of  the  Cleve- 
land Twist  Drill  Co.  have  led  to  the  conclusion  that,  in  estab- 
lishing the  best  conditions  of  operation  for  a  given  job,  it  is 
well  to  start  carbon  steel  twist  drills  under  the  following  con- 
ditions of  speed  and  feed  until  more  definite  data  are  available 
as  to  the  maximum  speed  and  feed  which  can  properly  be  em- 
ployed for  the  operation  under  consideration. 

When  drilling  machine  steel,  use  a  peripheral  speed  of  30  feet 
per  minute;  for  cast  iron,  use  a  speed  of  35  feet  per  minute; 
and  for  brass,  use  a  speed  of  60  feet  per  minute.  In  each  case, 
a  feed  of  from  0.004  to  0.007  mcn  Per  revolution  should  be  em- 
ployed for  drills  up  to  \  inch  in  diameter,  while  for  larger  sizes 


84  MODERN  DRILLING  PRACTICE 

the  feed  should  be  from  0.005  to  °-OI5  mcn  Per  revolution.  In 
the  case  of  high-speed  steel  drills,  the  preceding  rates  of  speed 
should  be  increased  from  100  to  125  per  cent,  while  the  same 
rates  of  feed  are  employed.  The  Standard  Tool  Co.  recommends 
starting  high-speed  steel  drills  at  a  peripheral  speed  of  from  50 
to  70  feet  per  minute  for  wrought  iron  or  steel,  and  from  60  to 
80  feet  per  minute  for  cast  iron,  or  at  140  feet  per  minute  for 
brass.  The  feeds  recommended  are  0.004  inch  per  revolution  for 
a  yg-inch  drill  in  wrought  iron  or  steel,  0.005  inch  per  revolution 
for  a  J-inch  drill,  0.008  inch  per  revolution  for  a  f-inch  drill, 
o.oio  inch  per  revolution  for  a  i-inch  drill,  and  0.015  inch  per 
revolution  for  a  i^-inch  drill. 

The  Detroit  Twist  Drill  Co.  states  that  high-speed  steel  drills 
can  often  be  run  efficiently  at  over  100  feet  per  minute  in  cast 
iron,  but  that  better  results  will  usually  be  obtained  at  from 
60  to  70  feet  per  minute.  In  establishing  the  proper  conditions 
for  a  given  drilling  operation,  a  freshly  ground  drill  of  a  given 
size  should  be  tested  at  each  of  the  two  speeds  provided  by  the 
machine  above  and  below  that  which  is  necessary  to  give  a 
cutting  speed  of  70  feet  per  minute,  and  then  each  successive 
feed  provided  on  the  machine  should  be  tried  until  one  is  found 
at  which  the  drill  will  run  without  slowing  down  the  machine 
or  injuring  the  drill  during  a  period  of  one  hour's  operation, 
which  is  the  standard  shop  interval  during  which  a  drill  should 
operate  without  requiring  grinding.  It  might  be  thought  that 
this  would  require  considerable  time,  but,  as  a  matter  of  fact, 
the  establishment  of  speeds  and  feeds  by  this  method  can  be 
quickly  accomplished  and  the  saving  will  more  than  compen- 
sate for  the  time  spent  in  determining  the  most  efficient  con- 
ditions of  operation  where  there  are  a  large  number  of  parts 
to  be  drilled. 

For  drilling  wrought  iron  or  steel,  the  drill  should  be  started 
at  a  peripheral  speed  of  from  50  to  70  feet  per  minute,  for  cast 
iron  the  speed  should  be  from  60  to  80  feet  per  minute,  and  for 
brass,  from  100  to  150  feet  per  minute.  Under  favorable  con- 
ditions, the  feed  should  be  0.004  mch  Per  revolution  for  a  T^-inch 
drill  in  wrought  iron  or  steel;  0.005  inch  per  revolution  for  a 


SPEEDS  AND   FEEDS  FOR  DRILLING  85 

J-inch  drill;  0.008  inch  for  a  |-inch  drill;  o.oio  inch  for  a  i-inch 
drill;  and  0.015  mcn  f°r  a  2-inch  drill.  If  the  drill  breaks  or 
chips  on  the  cutting  edges,  the  rate  of  feed  should  be  re- 
duced. 

Starting  with  any  of  the  preceding  speeds  and  feeds  which 
have  been  recommended  by  different  authorities,  the  operator 
carefully  notes  the  condition  of  the  drill  after  it  has  been  work- 
ing for  some  time.  If  the  drill  shows  a  tendency  to  wear  away 
on  the  outside,  it  is  running  too  fast,  while  if  it  breaks  or  chips 
on  the  cutting  edges,  the  feed  is  probably  too  heavy  for  the  work 
required.  A  little  careful  experimenting  in  this  way,  making 
changes  gradually  according  to  indications  which  are  shown  after 
working  for  some  time,  will  usually  result  in  securing  a  combi- 
nation of  speed  and  feed  which  will  be  the  means  of  obtaining 
something  approaching  the  maximum  possible  production.  It 
will,  of  course,  be  obvious  that,  to  obtain  a  given  peripheral 
cutting  speed,  the  number  of  revolutions  per  minute  must  differ 
according  to  the  size  of  the  drill  which  is  being  used.  This  is 
the  reason  for  running  very  small  drills  at  extremely  high  speeds 
in  order  to  have  them  working  under  conditions  which  approxi- 
mate the  required  cutting  speed  for  the  material  that  is  being 
machined.  For  the  convenience  of  users  of  twist  drills  and 
other  rotary  cutting  tools,  tables  are  available  which  show  the 
number  of  revolutions  per  minute  at  which  a  given  size  of  drill 
should  be  run  in  order  to  obtain  the  required  cutting  speed.  In 
Tables  i  and  2  the  diameters  of  drills  are  given  in  the  left-hand 
column,  while  peripheral  cutting  speeds  in  feet  per  minute  are 
noted  at  the  top  of  the  table.  By  finding  the  intersection  of 
horizontal  and  vertical  lines  through  the  given  drill  diameter 
and  the  required  cutting  speed,  the  number  of  revolutions  per 
minute  at  which  the  drill  must  be  run  in  order  to  obtain  this 
speed  will  be  found.  Table  3  gives  the  decimal  equivalents  of 
nominal  sizes  of  drills,  and  will  be  found  useful  when  calcu- 
lating the  peripheral  cutting  speed  of  drills  of  various  sizes; 
this  table  also  shows  the  relation  of  the  different  sizes  of 
drills,  which  are  designated  by  letters  and  numbers,  as  com- 
pared to  the  fractional  sized  drills. 


86 


MODERN  DRILLING  PRACTICE 


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SPEEDS  AND   FEEDS  FOR  DRILLING 


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88 


MODERN  DRILLING  PRACTICE 


Table  3.    Decimal  Equivalents  of  Nominal  Sizes  of  Drills 


Inch 

Wire 
Gage 

Decimals 
of  an 
Inch 

Inch 

Wire 
Gage 

Decimals 
of  an 
Inch 

Inch 

Let- 
ter 
Sizes 

Decimals 
of  an  Inch 

Inch 

Decimals 
of  an  Inch 

80 

0.0135 

35 

O.IIOO 

G 

0.2610 

3A 

0.7500 

79 

0.0145 

34 

O.IIIO 

I|fc 

0.2656 

4%4 

0.7656 

Ht 

0.0156 

33 

0.1130 

H 

0.2660 

2^2 

0.7813 

78 

0.0160 

32 

0.1160 

I 

0.2720 

•& 

0.7969 

77 

0.0180 

31 

O.I2OO 

] 

0.2770 

13/ie 

0.8125 

76 

O.O2OO 

M 

0.1250 

K 

0.2810 

53/64 

0.8281 

75 

O.O2IO 

30 

0.1285 

%2 

0.2813 

2J$2 

0.8438 

74 

•  o  .  0225 

29 

'  0.1360 

L 

0.2900 

5%4 

0.8594 

73 

O.O240 

28 

0.1405 

M 

0.2950 

% 

0.8750 

72 

o  .  0250 

%4 

0.1406 

\%i 

0.2969 

*%\ 

0.8906 

7i 

O.O26O 

27 

0.1440 

N 

0.3020 

2?$2 

.9063 

70 

0.0280 

26 

0.1470 

Me 

0.3125 

S%4 

.9219 

69 

0.0293 

25 

0.1495 

O 

0.3160 

>$i« 

•  9375 

68 

O.O3IO 

24 

0.1520 

P 

0.3230 

•J*4 

•  9531 

Ha 

0.0313 

23 

0.1540 

2^4 

0.3281 

»Ha 

.9688 

67 

O.O32O 

%1 

0.1563 

Q 

0.3320 

6%4 

.9844 

66 

O.O33O 

22 

0.1570 

R 

0.3390 

I 

.0000 

65 

0.0350 

21 

0.1590 

»HJ 

0.3438 

1^4 

.0156 

64 

0.0360 

2O 

0.1610 

S 

0.3480 

iHa 

.0313 

63 

0.037D 

19 

0.1660 

T 

0.3580 

i%i 

.0469 

62 

O.O38O 

18 

0.1695 

2964 

0.3594 

ific 

.0625 

61 

0.0390 

lHi 

0.1719 

U 

0.3680 

I%4 

.0781 

60 

O.04OO 

17 

0.1730 

H 

0.3750 

I3/^ 

-0938 

59 

O.O4IO 

16 

0.1770 

V 

0.3770 

I%4 

.1094 

58 

O.O42O 

15 

0.1800 

0.3819 

I1/^ 

.1250 

57 

0.0430 

14 

o  .  1820 

W 

0.3860 

I%1 

.1406 

56 

o  .  0465 

13 

0.1850 

2^64 

0.3906 

iHa 

.1563 

%4 

0.0469 

9ia 

0.1875 

X 

0.3970 

I»H4 

.1719 

55 

0.0520 

12 

0.1890 

Y 

0.4040 

iMa 

•  i875 

54 

0.0550 

ii 

0.1910 

i  Ha 

0.4063 

l!%4 

.2031 

53 

0.0595 

IO 

0.1935 

Z 

0.4130 

1^2 

.2188 

Me 

0.0625 

9 

0.1560 

2%4 

0.4219 

IJH4 

•  2344 

*J~ 

0.0635 

8 

0.1990 

Me 

0.4375 

iK 

.2500 

51 

0.0670 

7 

0.2010 

2%4 

0.4531 

IJ^4 

.2656 

50 

0.0700 

iHi 

0.2031 

1^2 

0.4688 

I%2 

.2813 

49 

0.0730 

6 

0.2040 

8  H* 

0.4844 

I1  9^4 

.2969 

48 

0.0760 

5 

0.2055 

H 

0.5000 

iMe 

.3125 

%4 

0.0781 

4 

0.2090 

3%4 

c.5156 

I2H4 

.3281 

47 

0.0785 

3 

0.2130 

IJfa 

0.5313 

I»^2 

.3438 

46 

0.0810 

^ 

0.2188 

3%4 

0.5469 

I»H4 

•  3594 

45 

0.0820 

2 

0.2210 

Hi 

0.5625 

iH 

•  3750 

44 

0.0860 

I 

0.2280 

3%4 

0.5781 

I2%4 

.3906 

43 

0.0890 

!%2 

0.5938 

I13^2 

.4063 

42 

0.0935 

Letter 

3%4 

0.6094 

I»%4 

.4219 

Ha 

0.0938 

Sizes 

% 

o  .  6250 

iM« 

•  4375 

41 

0.0960 

A 

0.2340 

4  Hi 

0.6406 

I2%4 

•  4531 

40 

0.0980 

15/64 

0.2344 

21/^2 

0.6563 

i^Hz 

.4688 

39 

0.0995 

B 

0.2380 

4%4 

0.6719 

I3H4 

'       .4844 

38 

0.1015 

C 

O.242O 

'M6 

0.6875 

rH 

.5000 

37 

0.1040 

D 

0.2460 

•5*4 

0.7031 

I3%4 

.5156 

36 

0.1065 

N 

E 

0.2500 

2%2 

0.7188 

11^2 

.5313 

& 

0.1094 

F 

0.2570 

*%4 

0.7344 

I3  ^4 

.5469 

SPEEDS  AND   FEEDS  FOR  DRILLING  89 

Automatic  Speed  Adjustment  for  Drilling  Machine.  —  Where 
quick-change  chucks  are  used  to  facilitate  changing  tools  for 
the  performance  of  a  sequence  of  operations  on  a  piece  of  work, 
it  is  apparent  that  provision  must  be  made  for  changing  the 


Fig.  i.  Radial  Drilling  Machine  equipped  with  Automatic  Control 
for  Variable-speed  Motor  Drive  to  assure  Proper  Cutting  Speed 
for  all  Tools 

spindle  speed  of  the  drilling  machine  for  different  sizes  of  tools, 
or  else  some  of  these  tools  will  have  to  be  driven  below  the  most 
efficient  speeds  for  such  sizes  of  drills,  counterbores,  etc.  In 
Fig.  i  is  shown  a  radial  drilling  machine  equipped  with  variable- 
speed  motor  drive  and  means  of  automatically  changing  the 
speed  so  that  approximately  the  proper  speed  may  be  obtained 


MODERN  DRILLING  PRACTICE 


for  each  size  of  tool  that  is  used.  The  machine  is  shown  at 
work  in  the  shops  of  the  Universal  Motor  Co.,  and  the  automatic 
speed-changing  device  was  designed  by  L.  J.  Monahan,  presi- 
dent of  the  firm.  Referring  to  Fig.  2,  it  will  be  seen  that  the 
drilling  machine  is  equipped  with  one  of  the  "  Magic  "  chucks  A 
made  by  the  Modern  Tool  Co.,  and  the  collets  B  which  enter 
this  chuck  are  each  provided  with  a  pin  C  which  extends  up 
through  the  chuck  body  and  engages  the  bottom  of  pin  D. 
These  pins  C  are  made  of  different  lengths  and  automatically 
adjust  a  speed-controlling  rheostat  E  to  provide  for  regulating 


Machinery 


Fig.  2. 


Method  of  obtaining  Automatic  Control  of  Variable- 
speed  Motor  Drive 


the  speed  of  motor  F  to  give  the  proper  spindle  speed  for  the 
particular  size  of  drill  or  other  tool  being  used.  In  this  way 
there  is  an  assurance  of  each  tool  being  driven  at  its  most  efficient 
speed.^  By  making  the  speed  change  automatically,  no  demand 
is  made  upon  the  operator,  and,  therefore,  there  is  no  loss  of 
time  in  speed  changing;  also  the  "Magic"  chuck  enables  tools 
to  be  changed  without  stopping  the  rotation  of  the  drilling  ma- 
chine spindle. 

Critical  Drilling  Speeds.  —  In  experimenting  to  determine  the 
number  of  revolutions  per  minute  at  which  a  drill  will  have  the 
greatest  productive  capacity,  some  interesting  results  are  se- 
cured. Researches  which  were  made  at  the  plant  of  Baker 


SPEEDS  AND   FEEDS   FOR  DRILLING 


Bros.,  with  the  view  of  securing  data  required  in  connection 
with  the  design  of  their  drilling  machines,  showed  that  there  are 
certain  critical  speeds  at  which  a  twist  drill  will  have  a  satis- 
factory rate  of  production,  while  there  are  other  speeds  —  often 


8 

J 

^ 

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•0- 

to 

C 

\R 

| 

FC 

R 

\p 

G, 

7 

> 

>J 

1A 

HICKl    | 

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xj. 

4 

DRlLt. 

/ 

~^ 

s.NO.2 

7 

s 

^ 

6 

/ 

1 

N  INCHES  PER  MINUTE 

£t.  cn 

N 

„ 

/E 

RY 

LC 

s 

C 

\R 

30 

N 

\ 

/ 

^x 

x  E 

ESSEM 

R 

MACHINE 

ST 

EEL, 

Mj 

j 

1' 

™ 

•IIO 

yA 

'OR 

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\ 

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^ 

7 

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3 

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1 

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v\ 

1 

£ 

x 

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nery 

0               100             200              300             400              500             600             7( 

SPEED  IN  REVOLUTIONS  PER  MINUTE                                     MdCM 

Fig.  3. 


Diagram  showing  Effect  of  Critical  Speeds  on 
Penetration-speed  Curves 


lying  between  two  rates  of  speed  where  the  production  is  satis- 
factory —  at  which  the  drill  will  fail  to  give  anything  approach- 
ing satisfactory  results.  This  condition  is  clearly  shown  by 
Fig.  3,  which  is  plotted  with  data  taken  from  original  tests. 
These  investigations  were  made  several  years  ago,  so  that, 
while  the  condition  shown  by  this  set  of  curves  is  an  established 
fact,  the  rates  of  speed  and  feed  are  lower  than  would  be  used 


92  MODERN  DRILLING  PRACTICE 

in  conducting  similar  tests  at  the  present  time.  The  point 
brought  out  by  this  diagram  is  the  remarkable  increase  in  pro- 
duction which  can  be  secured  by  increasing  the  speed.  The 
curves  are  plotted  for  the  maximum  feed  at  which  the  stock  was 
successfully  drilled  without  destroying  the  drill;  at  the  next 
higher  feed  the  drill  would  be  destroyed.  Curve  No.  2  shows 
that  the  drill  would  give  a  far  greater  production  without  failing 
at  200  revolutions  per  minute  than  it  would  at  250  revolutions 
per  minute,  and  also  that  it  would  give  a  much  greater  produc- 
tion if  the  speed  were  still  further  increased  to  400  revolutions 
per  minute. 

This  is  of  particular  interest  in  connection  with  the  sugges- 
tions made  for  experimenting  to  determine  the  speed  at  which 
a  given  drilling  operation  may  be  performed  to  secure  the 
greatest  possible  output.  Should  it  happen  that  the  drilling 
machine  operator  has  reason  to  believe  that  the  speed  he  is 
using  is  too  low,  but  finds  that  a  moderate  increase  in  speed 
results  in  an  even  less  satisfactory  rate  of  production,  he  is 
justified  in  believing  that,  if  the  speed  rate  of  penetration  were 
plotted  in  the  form  of  a  curve  shown  in  Fig.  3,  the  "  speed- 
penetration  "  curve  has  taken  one  of  those  peculiar  dips  ex- 
hibited in  this  illustration,  and  that  a  still  further  increase 
in  speed  will  probably  result  in  determining  a  rate  at  which 
the  desired  production  will  be  attained.  If  such  is  the  case, 
it  is  obvious  that  correction  of  the  original  cause  for  the  un- 
satisfactory rate  of  production  will  be  made  by  a  considerable 
increase  in  speed  and  not  by  making  a  reduction  in  speed, 
as  might  be  inferred  from  the  fact  that  advancing  a  little  from 
the  original  speed  at  which  production  was  unsatisfactory 
showed  that  even  less  desirable  results  were  being  obtained. 

Recently  a  well-known  manufacturing  establishment  had 
an  investigating  committee  working  for  over  two  years  on 
the  development  of  a  table  of  speeds  and  feeds  for  use  in  con- 
nection with  different  sizes  of  drills  working  in  various  ma- 
terials. The  result  of  this  investigation  is  presented  in  Tables 
4  and  5 ,  and  although  it  is  not  claimed  that  the  data  presented 
can  be  followed  without  modification,  it  is  claimed  that  the 


SPEEDS  AND   FEEDS  FOR  DRILLING 


93 


Table  4.    Speeds  and  Feeds  for  High-speed  Drills  Working  in  Various 

Metals 


Size  of 
Drill, 
Inch 

Feed  per 
Rev.,  Inch 

Bronze, 
Brass, 
300  Feet. 
R.P.M. 

Cast 
Iron, 
Anneal- 
ed, 
i?oFeet, 

Hard 
Cast 
Iron, 
80  Feet, 

Mild 
Steel, 
i2oFeet, 
R.P.M. 

Drop- 
forging, 
60  Feet, 
R.P.M. 

Malle- 
able 
Iron, 
90  Feet, 

Tool 

Steel, 
60  Feet, 
R.P.M. 

Cast 
Steel, 
40  Feet, 
R.P.M. 

R.P.M. 

R.P.M. 

R.P.M. 

He 

0.003 

4880 

3660 

3660 

244O 

M 

O   OOA 

ciSs 

244O 

1660 

o 
1830 

274^ 

o 

18^0 

4t^L^\J 

I  22O 

H« 

•  x-/v^it 
O   OOS 

0  ***O 

34^6 

«6^«fM 

1626 

o 
2440 

X(-'O 

I2IO 

*  /MO 

1830 

•L*-Jo 
1  2  2O 

80  7 

M 

V    ^^  J 

0.006 

4575 

OHO 

2593 

I22O 

«»4ffifW 

l830 

9J5 

XVJ^'J 

1375 

915 

OW/ 

610 

Ms 

0.007 

3660 

2074 

976 

1464 

732 

1138 

732 

490 

N 

0.008 

3050 

1728 

813 

I22O 

610 

915 

610 

407 

Ma 

0.009 

2614 

1482 

698 

1046 

522 

784 

522 

348 

J/i 

O.OIO 

2287 

1296 

610 

915 

458 

636 

458 

305 

tt 

O.OII 

1830 

1037 

488 

732 

366 

569 

366 

245 

% 

O.OI2 

!525 

864 

407 

610 

3°5 

458 

305 

203 

H 

0.013 

1307 

74i 

349 

523 

261 

392 

261 

i74 

I 

0.014 

H43 

648 

305 

458 

229 

349 

229 

153 

IN 

0.016 

9i5 

519 

244 

366 

183 

275 

183 

122 

iH 

0.016 

762 

432 

204 

305 

153 

212 

153 

IO2 

i% 

0.016 

654 

37i 

175 

262 

131 

196 

131 

87 

2 

0.016 

57i 

323 

153 

229 

H5 

172 

"5 

77 

Table  5.     Speeds  and  Feeds  for  Carbon  Steel  Drills  Working  in  Various 

Metals 


Size  of 
Drill, 
Inch 

Feed  per 
Rev.,  Inch 

Bronze, 
Brass, 
300  Feet, 
R.P.M. 

Cast 
Iron, 
Anneal- 
ed, 
85  Feet, 
R.P.M. 

Hard 
Cast 
Iron, 
40  Feet, 
R.P.M. 

Mild 
Steel, 
60  Feet, 
R.P.M. 

Drop- 
forging, 
30  Feet, 
R.P.M. 

Malle- 
able 
Iron, 
45  Feet, 
R.P.M. 

Tool 
Steel, 
30  Feet, 
R.P.M. 

Cast 
Steel, 
20  Feet, 
R.P.M. 

H< 

0.003 

5185 

2440 

3660 

1830 

2745 

1830 

I22O 

Mi 

0.004 

4575 

2593 

I22O 

1830 

915 

1375 

915 

610 

3/i6 

0.005 

3050 

1728 

813 

I22O 

610 

915 

610 

407 

H 

0.006 

2287 

1296 

610 

915 

458 

636 

458 

305 

5/i6 

0.007 

1830 

1037 

488 

732 

366 

569 

366 

245 

% 

0.008 

1525 

864 

407 

610 

305 

458 

305 

203 

V\6 

0.009 

1307 

741 

349 

523 

261 

392 

261 

174 

l/2 

O.OIO 

H43 

648 

305 

458 

229 

343 

229 

153 

% 

O.OII 

9i5 

519 

244 

366 

183 

275 

183 

122 

H 

O.OI2 

762 

'432 

204 

305 

153 

212 

153 

102 

H 

0.013 

654 

371 

175 

262 

131 

196 

131 

87 

i 

0.014 

57i 

323 

153 

229 

US 

172 

H5 

77 

IH 

0.016 

458 

260 

122 

183 

92 

138 

92 

61 

m 

0.016 

38i 

216 

IO2 

153 

77 

106 

77 

51 

iH 

0.016 

327 

1  86 

88 

131 

66 

98 

66 

44 

2 

0.016 

286 

162 

87 

"5 

58 

86 

58 

39 

94  MODERN  DRILLING  PRACTICE 

thousands  of  tests  which  were  made  during  the  period  over 
which  these  data  were  secured  have  led  to  results  which  may 
safely  be  regarded  as  an  average  maximum  of  the  rate  of  speed 
and  feed  under  which  a  drilling  machine  may  be  operated. 
These  tables  are  copyrighted  by  the  Henry  &  Wright  Mfg.  Co., 
and  the  tests  were  made  on  a  special  drilling  machine  built  by 
this  company. 

In  starting  to  work  on  a  new  job  the  operator  of  the  drill- 
ing machine  will  use  the  speed  and  feed  shown  in  these  tables, 
but  should  he  find  that  the  drill  shows  a  tendency  to  wear 
around  its  periphery  or  that  there  is  a  considerable  amount 
of  chipping  along  the  cutting  edges  of  the  drill,  it  indicates 
that  the  speed  or  feed  is  too  heavy,  and  so  the  required  adjust- 
ment of  operating  conditions  must  be  made.  In  the  plant 
where  these  data  were  obtained,  the  investigating  committee 
reported  that  the  installation  of  machines  capable  of  operating 
under  these  conditions  of  speed  and  feed  would  represent  a 
saving  of  $30,000  a  year.  The  speeds  recommended  are  rather 
high,  and  if  twist  drills  are  unable  to  stand  them,  the  drill 
manufacturers  should  be  notified,  as  it  is  claimed  that  any 
responsible  maker  can  furnish  suitable  drills  for  use  under 
these  conditions  if  he  is  required  to  do  so.  The  speeds  are 
also  too  high  for  machines  equipped  with  plain  bearings,  but 
properly  constructed  machines  with  ball  bearings  will  easily 
stand  up  under  such  conditions  of  operations. 

After  reading  the  preceding  suggestions  concerning  the  most 
efficient  speeds  and  feeds  at  which  drilling  operations  can  be 
performed,  the  reader  will  naturally  be  impressed  by  the  dif- 
ference in  these  recommendations,  and  noting  that  they  are 
made  by  men  who  have  equal  opportunities  of  determining 
the  required  information,  he  will  ask  himself  which  conditions 
are  likely  to  produce  the  best  results  in  his  own  shop.  The 
difference  in  these  recommendations  is  probably  due  to  the 
fact  that  there  are  so  many  variables  which  enter  into  the 
performance  of  drilling  operations  that  different  combinations 
of  variable  conditions  enable  the  most  satisfactory  results  to 
be  obtained  when  using  speeds  and  feeds  which  differ  sub- 


SPEEDS  AND   FEEDS  FOR  DRILLING  95 

stantially.  Regardless  of  the  reason,  it  is  a  matter  of  fact 
that  different  men  have  found  that  the  most  satisfactory  re- 
sults are  obtained  when  running  their  drilling  machines  under 
conditions  of  speed  and  feed  which  differ  substantially  when 
drilling  a  given  size  of  hole  in  the  same  material.  Such  being 
the  case,  the  best  advice  which  can  be  given  to  the  man  who 
is  trying  to  improve  conditions  in  his  drilling  department  is 
to  adopt  the  method  of  experimenting  with  trial  speeds  and 
feeds  —  adopting  those  trial  speeds  and  feeds  recommended  in 
the  preceding  discussion  —  until  he  has  found  the  conditions 
of  speed  and  feed  which  give  the  most  satisfactory  results  on 
his  work. 

High  Speeds  of  Modern  Drilling  Machines.  —  Machine  tool 
builders  are  now  making  drilling  machines  fully  equipped  with 
ball  bearings  so  that  they  are  adapted  for  operation  at  speeds 
which  would  have  been  utterly  impossible  of  attainment  a  few 
years  ago.  For  instance,  the  Leland-Gifford  Co.  builds  a  ma- 
chine which  is  adapted  for  operation  at  speeds  of  from  1 1 ,000  to 
15,000  revolutions  per  minute,  and  the  same  speeds  are  recom- 
mended for  use  on  a  bench  drilling  machine  recently  brought 
out  by  the  Fenn  Mfg.  Co.  Other  machinery  builders  are  mak- 
ing high-speed  drilling  machines.  Driving  twist  drills  at  such 
speeds  means  that  the  drilling  operation  is  practically  instan- 
taneous; in  fact,  the  speed  at  which  holes  may  be  drilled  is 
often  equal,  if  not  in  excess,  of  the  speed  at  which  the  same 
work  could  be  done  on  a  power  press.  It  is  this  constant  in- 
crease in  the  speed  of  drilling,  with  the  constant  reduction  of  the 
ratio  between  "  drilling  time  "  and  "  setting-up  time,"  which 
has  emphasized  the  fact  that,  in  order  to  approach  the  maximum 
rate  of  production,  the  user  of  high-speed  drilling  machines  must 
design  his  work-holding  fixtures  in  such  a  way  that  work  may 
either  be  set  up  in  indexing  fixtures  while  the  drilling  operation 
is  being  performed,  or,  if  this  is  not  feasible,  the  clamping  devices 
on  fixtures  must  be  so  made  that  a  minimum  amount  of  time 
is  consumed  in  securing  the  work  in  place  ready  to  be  drilled. 

Several  important  advantages  are  secured  through  drilling 
at  high  speed,  and  this  is  particularly  the  case  with  small 


96  MODERN  DRILLING  PRACTICE 

sized  drills,  which  are  likely  to  break,  and  also  with  high-speed 
steel  drills.  The  reasons  for  this  are  as  follows:  In  the  case  of 
small  drills  operated  in  sensitive  drilling  machines  equipped 
with  hand  feed,  running  the  drill  at  high  speed  makes  it  im- 
probable that  the  operator  will  impose  an  excessive  feed  on  the 
drill,  because,  in  the  case  of  a  drill  which  is  running  at  from 
10,000  to  15,000  revolutions  per  minute,  it  would  be  necessary 
to  pull  the  feed-lever  down  extremely  fast  in  order  that  the  feed 
for  any  one  revolution  of  the  drill  would  be  sufficient  to  impose 
a  stress  in  the  steel  which  would  be  in  excess  of  the  maximum 
that  the  strength  of  the  drill  is  capable  of  withstanding.  A 
further  explanation  for  the  increased  strength  of  a  drill  when 
running  at  high  speed  is  that  where  an  excessive  amount  of 
feed  pressure  tends  to  bend  the  drill  slightly  when  running  at 
high  speed,  the  length  of  time  that  any  set  of  fibers  in  the  drill 
is  subjected  to  stress  is  so  short  that  the  danger  of  breaking  may 
be  less  than  if  the  load  remains  on  such  fibers  for  a  greater  length 
of  time.  This  is,  of  course,  an  unsettled  question  and  is  advanced 
in  the  form  of  a  hypothesis  rather  than  a  statement  of  fact;  in 
any  case,  the  question  is  an  interesting  one. 

Effect  of  High  Speeds  on  High-speed  Steel  Drills. —  With 
high-speed  steel  drills,  there  is  an  increase  in  strength  and  dur- 
ability when  running  at  high  speed  which  can  be  explained  in  a 
more  definite  way.  At  a  speed  of,  say,  10,000  revolutions  per 
minute,  the  frictional  resistance  and  tendency  for  the  drill  to 
become  heated  are  far  more  pronounced  than  where  the  drill  is 
being  operated  at,  say,  350  revolutions  per  minute.  It  is  a  well- 
known  fact  that  many  classes  of  high-speed  steel  are  tough  and 
hard  even  at  temperatures  corresponding  to  a  dull  red  heat; 
conversely,  such  steels  are  inclined  to  be  quite  brittle  at  low 
temperatures.  As  a  result,  the  increase  in  frictional  resistance 
resulting  from  the  operation  of  a  high-speed  steel  drill  at  the 
higher  speed  results  in  increasing  its  temperature,  with  a  corre- 
sponding improvement  in  the  toughness  and  hardness  of  the 
steel.  Consequently,  it  is  obvious  that  a  high-speed  steel  drill 
should  give  better  results  when  working  at  speeds  which  cause 
it  to  become  heated  slightly  while  in  operation. 


SPEEDS   AND   FEEDS   FOR  DRILLING  97 

This  naturally  leads  to  two  points  which '  should  be"  observed 
in  caring  for  high-speed  steel  drills  in  order  to  enable  them 
to  give  the  best  possible  results.  In  cold  weather  it  will  be 
found  advantageous  to  warm  the  drills  slightly  before  they 
are  placed  in  service.  Such  an  increase  in  temperature  will 
be  the  means  of  taking  much  of  the  brittleness  out  of  the  metal, 
thus  avoiding  danger  of  the  drill  breaking  before  it  has  had 
time  to  become  warmed  up  through  frictional  resistance  between 
the  tool  and  work  which  is  being  drilled.  Another  point  which 
is  sufficiently  important  to  merit  careful  consideration  is  that 
some  makes  of  high-speed  steel  are  likely  to  be  damaged  if 
suddenly  quenched  in  cold  water.  In  grinding  a  drill,  some 
operators  will  plunge  the  point  into  water,  and  when  this  is 
done  there  is  danger  of  introducing  cracks  in  the  cutting  edge; 
these  may  not  be  of  sufficient  magnitude  to  show  to  the  naked 
eye,  but  when  the  drill  is  put  to  work  trouble  is  likely  to  be 
experienced  at  once  through  the  chipping  away  of  steel  along 
the  lips  of  the  drill. 

Feed  Pressure  required  for  Drilling.  —  In  Fig.  4  there  is 
shown  a  special  drilling  machine  which  was  built  for  use  in  the 
laboratory  of  the  Standard  Tool  Co.  for  conducting  experimental 
work  on  twist  drills.  This  machine  is  symmetrically  designed 
on  both  sides  of  an  axis  corresponding  to  the  axis  of  the  twist 
drill  which  is  being  tested,  this  arrangement  tending  to  equalize 
all  stresses  that  are  set  up  in  the  frame  of  the  machine  and  to 
cause  the  thrust  of  the  drill  to  be  vertically  downward.  In 
the  case  of  an  ordinary  drilling  machine  with  the  overhanging 
type  of  frame,  there  is  a  cantilever  action  which  causes  the 
thrust  of  the  drill  to  be  separated  into  two  components.  On 
this  special  drilling  machine  shown  in  Fig.  4,  the  bedplate 
which  supports  the  work  rests  on  a  1 2-inch  piston,  which  is 
ground  to  a  sliding  fit  in  a  cylinder  filled  with  oil.  Arms  and 
counterweights  attached  to  each  side  of  the  piston  compensate 
for  the  total  weight  of  the  piston  and  bedplate,  so  that  gages 
connected  to  the  oil  cylinder  indicate  the  pressure  actually 
applied  by  the  drill,  the  gages  being  calibrated  to  indicate  the 
total  pressure  on  the  12 -inch  ram.  Two  gages  are  used,  one 


98 


MODERN  DRILLING  PRACTICE 


of  which  reads  up  to  3000  pounds,  while  the  other  reads  up  to 
15  tons. 

The  spindle  and  feed  mechanisms  are  driven  by  two  inde- 
pendent electric  motors.    For  driving  the  spindle,  the  motor  is 


Fig.  4. 


Special  Drilling  Machine  used  in  Laboratory  of 
Standard  Tool  Co. 


mounted  at  the  top  of  the  machine  with  the  armature  shaft 
in  a  vertical  position,  so  that  it  may  be  direct-connected  to 
the  spindle  of  the  drilling  machine.  The  feed  mechanism  is 
driven  by  a  motor  located,  at  the  right-hand  side  of  the  ma- 
chine, and  this  motor  is  connected  to  the  feed  through  a  sys- 
tem of  worm-gears  and  a  rack  and  pinion.  An  indicating  watt- 


SPEEDS  AND   FEEDS  FOR  DRILLING  99 

meter  in  each  circuit  shows  the  power  consumption,  and  each 
motor  is  furnished  with  an  independent  rheostat  by  which 
variations  in  speed  are  effected.  The  speeds  of  the  motors 
that  drive  the  spindle  and  feed  mechanism  are  indicated  by 
two  Warner  tachometers,  and  a  chart  has  been  developed  to 
give  the  rate  of  feed  for  different  speeds  of  the  motor  that  drives 
the  feed  mechanism. 

A  series  of  tests  was  conducted  on  this  machine  by  Paul 
Bedell  Starr  and  John  Millard  Marsh  to  secure  data  for  a 
thesis  presented  at  the  time  these  men  took  the  degree  of 
Bachelor  of  Science  in  mechanical  engineering  at  the  Case 
School  of  Applied  Science.  The  object  of  this  investigation 
was  principally  to  determine  the  feed  pressure  required  to 
drive  different  sizes  of  drills  under  various  conditions  of 
speed  and  feed.  That  very  little  reliable  data  were  available 
on  this  subject  was  shown  by  the  fact  that,  when  the  special 
drilling  machine  was-  first  built  by  a  firm  of  wide  experience 
in  the  design  and  construction  of  equipment  of  this  type,  a 
pressure  gage  reading  up  to  3000  pounds  was  provided.  At 
the  first  test,  using  a  i-inch  drill  at  a  normal  rate  of  feed,  the 
range  of  this  gage  was  shown  to  be  entirely  inadequate;  there- 
fore, a  gage  reading  up  to  15  tons  was  substituted,  which  proved 
suitable  for  the  service  required  of  it,  this  difference  in  gages 
showing  conclusively  that  the  knowledge  concerning  the  mag- 
nitude of  feed  pressures  was  not  at  all  definite. 

Five  series  of  tests  were  conducted  under  the  following  con- 
ditions: On  the  first  series,  the  clearance  angle  of  the  drills 
used  was  less  than  the  standard  12 -degree  clearance  adopted 
by  the  Standard  Tool  Co.,  which  furnished  the  twist  drills 
used  in  making  this  investigation.  On  the  second  series,  the 
clearance  angle  was  greater  than  the  standard  12  degrees.  On 
the  third  series,  the  drills  used  were  standard  in  every  respect. 
On  the  fourth  series,  the  web  thickness  of  the  drills  was  10 
per  cent  under  standard,  and  thinned  in  accordance  with  the 
practice  of  the  Standard  Tool  Co.  On  the  fifth  series,  the  web 
thickness  was  10  per  cent  above  standard.  The  first  series 
of  tests,  with  the  clearance  angle  less  than  the  standard  of 


100  MODERN  DRILLING  PRACTICE 

12  degrees,  showed  that  an  excessive  amount  of  feed  pressure 
was  required  to  operate  a  drill  ground  in  this  way,  such  a  result 
-being  entirely  expected,  because  the  cutting  edges  are  not 
given  free  play.  In  the  second  and  third  series  of  tests,  where 
the  clearance  angle  was  greater  than  the  standard  of  1 2  degrees, 
and  where  all  dimensions  of  the  drills  were  standard,  practically 
the  same  results  were  obtained  as  regards  feed  pressure,  which 
indicated  that  no  particular  advantage  was  obtained  by  in- 
creasing the  clearance  angle  beyond  12  degrees.  It  will  also  be 
recalled  that  such  an  increase  results  in  weakening  the  cutting 
edges  of  the  drill  and  introducing  a  tendency  for  them  to  be 
damaged  by  chipping. 

In  the  fourth  series  of  tests,  where  the  web  thickness  was 
reduced  10  per  cent,  there  was  a  noticeable  decrease  in  feed 
pressure,  which  indicates  that  advantages  are  to  be  secured 
through  thinning  the  point  of  the  drill,  provided  this  work 
is  carefully  done,  so  that  there  is  no  danger  of  weakening  the 
drill  sufficiently  to  cause  it  to  split  up  the  center.  For  the 
fifth  series  of  tests,  where  the  web  thickness  was  greater  than 
standard,  the  results  obtained  were  not  entirely  satisfactory, 
but,  under  these  conditions  of  operation,  it  is  fairly  safe  to 
assume  that  an  increase  in  feed  pressure  would  be  the  result. 
The  data  secured  from  these  tests  must  be  regarded  more  in 
the  light  of  indications  of  probable  results  from  varying  con- 
ditions of  operation  than  as  statements  of  fact  concerning 
results  actually  discovered,  because  lack  of  time  made  it  im- 
possible for  Mr.  Starr  and  Mr.  Marsh  to  carry  their  investiga- 
tions far  enough  to  secure  average  results;  and  average  results 
are  particularly  important  in  the  case  of  drilling  tests,  because 
of  the  numerous  variations  which  may  affect  results. 

Power  required  to  Drive  Drilling  Machines.  —  The  Detroit 
Twist  Drill  Co.  states  that  the  efficiency  of  most  drilling  ma- 
chines is  from  10  to  20  per  cent,  i.e.,  there  is  seldom  over  one- 
fifth  of  the  power  used  to  drive  a  drilling  machine  which  is 
transmitted  to  the  drill  point.  It  frequently  happens  that 
very  little  care  is  taken  to  see  that  drilling  machine  bearings 
are  properly  aligned  and  lubricated,  and  this  is  especially  true 


SPEEDS  AND   FEEDS J  FDR  DRILLING  101 

in  the  case  of  ball  thrust  bearings,  which  must  be  kept  in  good 
working  condition  in  order  to  be  effective  in  helping  the  ma- 
chine to  give  the  maximum  possible  service..  Attention  to  the 
upkeep  of  machine  bearings  is  exceptionally  important  in  the 
case  of  drilling  machines  operated  at  excessively  high  speed. 

Coolants  and   Lubricants  used  for   Drilling.  —  For   drilling 
operations,  satisfactory  results  can  usually  be  obtained  through 
the  use  of  one  of  the  soluble  oil  coolants,  for  all  classes  of  work 
where  the  length  of  chips  produced  is  not  very  great;  but  in 
cases  where  long  chips  are  formed,  there  is  a  rubbing  action 
produced  by  the  chips  sliding  over  the  lips  of  the  drill,  which 
produces  a  condition  analogous  to  that  of  a  machine  bearing, 
thus  making  it  necessary  to  apply  a  fluid  which  serves  the  com- 
bined purpose  of  lubricant  and  coolant.     The  following  is  an 
outline  of  lubricants  and  coolants  recommended  for  drilling  oper- 
ations in  various  classes  of  material,  and  the  lubricants  used  are 
recommended  in  the  order  in  which  they  are  named.     In  this  list 
"  cutting  compound  "  refers  to  any  satisfactory  brand  of  soluble 
oil  mixed  with  water,  in  accordance  with  the  manufacturer's  in- 
structions;  and  "  mineral  lard  oil  "  is  a  mixture  of  lard  oil  and 
light   petroleum   oil.     The   proportions   of   this   mixture   vary 
according  to  the  work,  but  one  part  of  lard  oil  to  two  parts  of 
petroleum  gives  a  mixture  that  is  well  suited  to  the  requirements 
of  many  average  drilling  operations.     For  drilling  high-carbon 
or  alloy  steel,  use  mineral  lard  oil  or  turpentine;    low-carbon 
steel,  mineral  lard  oil  or  cutting  compound;    cast  iron,  dry  or 
compressed  air;    wrought  iron,  cutting  compound  or  mineral 
lard  oil;  malleable  iron,  cutting  compound;  brass,  dry;  bronze, 
cutting  compound  or  dry;   copper,  mineral  lard  oil;   aluminum, 
kerosene,  beeswax,  or  tallow;   monel  metal,  cutting  compound; 
and  glass,  solution  of  camphor  in  turpentine. 


CHAPTER  V 
TYPES    OF   DRILLS   AND    DRILL    SOCKETS 

WHEN  the  purchasing  agent  of  an  industrial  plant  buys  twist 
drills,  he  should  bear  in  mind  the  fact  that  drills  are  merely 
the  means  to  attain  a  desired  end;  in  other  words,  he  is  really 
buying  drilled  holes  for  his  company.  Bearing  this  fact  in 
mind,  it  should  at  once  become  obvious  that  the  first  cost  of  a 
drill  is  likely  to  be  a  very  unimportant  matter,  as  the  ultimate 
criterion  of  the  price  of  the  tool  is  the  number  of  holes  which 
can  be  drilled  before  it  is  worn  out.  Such  being  the  case,  the 
wise  purchasing  agent  will  always  decide  upon  the  type  of  drill 
which  the  experience  of  men  in  the  manufacturing  departments 
of  his  company  has  shown  to  be  capable  of  giving  the  greatest 
amount  of  service  per  unit  cost. 

Two-fluted  Twist  Drills.  —  In  Fig.  i  are  shown  a  number  of 
different  types  of  drills,  some  of  which  are  commonly  used, 
while  others  represent  tools  developed  to  meet  the  requirements 
of  somewhat  special  classes  of 'work.  By  far  the  majority  of 
drilling  operations  are  performed  with  either  the  milled  twist 
drill  shown  at  A  or  the  so-called  flat-twisted  drill  which  is 
illustrated  at  B.  Both  of  these  types  have  certain  features  to 
commend  them  to  the  consideration  of  the  average  machine  shop 
manager.  It  is  generally  conceded  that  greater  accuracy  is 
secured  through  drilling  with  the  milled  twist  drill,  but  to  offset 
this  feature,  the  flat-twisted  drill  has  about  60  per  cent  more 
chip  clearance  in  the  flutes.  This  reduces  the  amount  of  power 
required  to  drive  the  drill,  and  also  makes  it  less  liable  that  the 
drill  will  be  broken.  To  offset  the  claim  for  greater  accuracy  of 
holes  drilled  with  milled  twist  drills,  the  claim  is  made  that,  as 
most  holes  have  to  be  reamed  before  their  accuracy  can  be 
depended  upon,  it  is  economical  to  take  advantage  of  the  lower 
price  of  the  flat-twisted  drill.  These  drills  are  made  by  twisting 
a  hot  flat  steel  bar  to  the  required  form 


HI  » 


c 


7G 


103 


104  MODERN   DRILLING   PRACTICE 

Three-  and  Four-fluted  Drills.  —  In  drilling  large  holes,  it 
will  sometimes  be  found  that  owing  to  an  insufficient  amount  of 
power  in  the  drilling  machine  on  which  the  operation  is  to  be 
performed,  or  for  some  other  reason,  a  hole  of  the  required  size 
cannot  be  drilled  at  one  operation.  In  such  cases,  a  small  hole 
is  drilled,  after  which  this  hole  is  drilled  out  to  the  required  size 
at  a  second  operation.  For  drilling  out  or  enlarging  the  hole, 
use  is  generally  made  of  either  a  three-  or  four-fluted  twist  drill 
of  the  forms  shown  at  C  and  D,  Fig.  i,  respectively.  These 
drills  are  not  adapted  for  drilling  holes  from  solid  metal,  but 
are  used  only  for  enlarging  a  hole  already  drilled. 

Straight-fluted  and  Flat  Drills.  —  While  drilling  brass  and 
thin  sheet  metal,  trouble  is  sometimes  experienced  through  the 
rake  of  the  cutting  edges  causing  the  drill  to  "  catch  "  or  "  dig 
in."  To  overcome  this  trouble,  profitable  use  may  be  made  of 
a  straight-fluted  drill  of  the  form  shown  at  E,  Fig.  i.  By 
having  two  straight  flutes  in  this  type  of  drill,  the  rake  angle  of 
the  cutting  edges  is  eliminated,  which  is  found  advantageous  for 
certain  classes  of  drilling  for  the  reasons  just  mentioned.  At 
F  and  G  there  are  shown  two  types  of  drills  which  are  employed 
for  the  same  general  classes  of  service  for  which  the  straight- 
fluted  drill  is  used,  although  the  form  of  the  two  latter  types  is 
quite,  different  from  that  of  the  drill  with  straight  flutes.  The 
type  of  drill  illustrated  at  F  is  known  as  a  flat  "  track  drill  " 
and  has  a  shank  of  suitable  form  for  use  in  a  blacksmith's  drill- 
ing machine;  the  flat  drill  shown  at  G  is  made  by  milling  away 
from  |  to  f  of  the  material  at  opposite  sides  of  a  piece  of  round 
steel  and  providing  two  cutting  edges  in  the  manner  shown. 
Such  a  drill  may  be  employed  for  drilling  brass  or  thin  sheet 
metal,  although  it  does  not  find  very  general  application  at  the 
present  time. 

The  Teat  Drill.  —  The  drill  shown  at  H,  Fig.  i,  is  generally 
known  as  a  "  teat "  drill.  This  type  of  drill  is  employed  for 
drilling  shallow  holes  where  it  is  required  to  have  a  flat  bottom 
in  the  hole,  or  the  teat  drill  may  be  used  for  drilling  out  the 
bottom  of  a  hole  produced  with  a  regular  twist  drill  in  order  to 
produce  a  flat  bottom. 


DRILLS  AND   DRILL   SOCKETS  105 

Center  Drill  and  Countersink.  —  At  /,  Fig.  i,  there  is  shown 
the  familiar  form  of  combination  center  drill  and  countersink 
which  is  used  for  producing  centers  in  which  twist  drills  may  be 
started,  for  centering  work  ready  to  be  set  up  on  a  lathe,  etc. 
This  tool  finds  such  general  application  in  the  machine  shop 
that  it  requires  no  further  discussion. 

Oil  Tube  Drills.  —  For  drilling  rather  deep  holes,  it  may  be 
found  that  trouble  will  be  experienced  in  getting  the  required 
quantity  of  oil  or  cutting  compound  to  the  point  of  the  drill, 
due  to  tendency  of  the  chips  to  carry  the  fluid  back  with  them 
before  it  reaches  the  bottom  of  the  hole.  To  overcome  this 
difficulty,  a  practice  is  made  of  using  what  are  known  as  "  oil 
tube  "  drills  which  are  provided  with  ducts  through  which  the 
lubricant  can  be  carried  right  to  the  cutting  point,  and  after 
doing  its  work  the  lubricant  and  chips  escape  through  the  flutes 
of  the  drill  in  the  usual  manner.  At  /,  Fig.  i ,  there  is  shown  the 
most  generally  used  type  of  oil  tube  drill  which  will  be  seen  to 
have  two  oil  ducts  running  through  the  metal  between  the  two 
flutes  in  the  drill. 

Hollow  and  Rifle  Barrel  Drills.  —  At  K  and  L,  Fig.  i,  there 
are  shown  types  of  drills  which  are  intended  for  drilling  deeper 
holes  than  could  be  handled  with  the  type  of  drill  shown  at  /. 
The  drill  point  at  K  is  known  as  a  "  hollow  "  drill  and  is  gen- 
erally used  in  a  lathe  where  the  work  revolves  and  the  drill 
remains  stationary.  There  is  a  hole  extending  lengthwise 
through  the  shank  to  connect  the  grooves  with  a  tubular  shank 
of  the  required  length  for  the  depth  of  hole  that  is  to  be  ma- 
chined in  the  work.  The  drill  point  is  threaded  and  fitted  into 
this  tube.  Drill  point  L  is  part  of  what  is  known  as  a  "  rifle 
barrel  "  drill.  This  steel  point  will  be  seen  to  have  a  crescent- 
shaped  duct  through  which  oil  is  forced  at  a  pressure  of  about 
800  pounds  per  square  inch  in  order  that  it  may  wash  the  chips 
back  through  the  straight  flute  at  the  side  of  the  drill.  This 
steel  drill  point  is  secured  to  the  end  of  a  tube  which  is  flattened 
at  one  side  in  order  that  oil  may  flow  through  the  tube  and 
escape  through  a  channel  outside  the  tube  which  corresponds 
in  shape  to  the  single  flute  in  the  drill  point.  It  will  be  ap- 


106  MODERN  DRILLING  PRACTICE 

parent  that  this  type  of  drill  has  one  cutting  lip  and  that  the 
clearance  surface  at  the  point  of  the  drill  is  backed  off  to  pro- 
vide the  necessary  clearance  for  the  cutting  edge. 

The  Cannon  Drill.  —  In  general  respects  the  deep-hole  drill 
shown  at  M  is  of  the  same  design  as  that  shown  at  L,  except 
that  the  cutting  edge  is  "  stepped  "  instead  of  straight,  in  order 
to  provide  for.  breaking  up  the  chips  into  such  a  form  that  they 
will  be  more  readily  cleared  from  the  hole.  This  is  known  as  a 
"  cannon  "  drill,  and  is  adapted  for  the  drilling  of  larger  sized 
holes  than  are  cut  by  the  drill  point  shown  at  L.  In  the  case 
of  the  last  three  types  of  drill  points  shown  in  this  illustration, 
the  work  revolves  and  the  drill  remains  stationary,  a  method  that 
produces  greater  accuracy. 

Spiral  and  Rake  Angles  of  Twist  Drills.  —  In  addition  to  the 
standard  dimensions  of  twist  drills  which  have  been  given  in 
connection  with  instructions  for  drill  grinding,  the  following 
angles  and  dimensions  are  fairly  standard:  At  the  point  of  the 
drill,  the  spiral  angle  of  the  flute  makes  an  angle  of  25  degrees 
with  the  center  line  of  the  drill,  and  this  angle  is  gradually 
decreased  to  20  degrees  at  the  end  of  the  flute  adjacent  to  the 
shank,  the  necessity  for  this  change  in  angle  being  to  increase 
the  chip  clearance  to  compensate  for  the  thickening  of  the  web 
of  the  drill.  Drills  are  not  made  of  the  same  diameter  from 
end  to  end,  but  decrease  from  the  point  toward  the  shank  by 
an  amount  varying  from  0.00025  to  0.0015  inch  per  inch  of 
length,  according  to  the  diameter  of  the  drill.  The  body  of 
the  drill  is  not  made  exactly  round,  it  being  general  practice  to 
back  off  or  relieve  the  land  of  the  drill  from  a  short  distance 
behind  the  leading  edge  of  each  flute.  The  thickness  of  the  web 
of  the-  drill  also  increases  from  the  point  to  the  shank  and  the* 
standard  rake  angle  for  the  cutting  edges  is  3^  degrees.  In  a 
drill  made  by  the  Detroit  Twist  Drill  Co.,  the  rake  angle  is 
increased  to  4!  degrees  and  the  spiral  angle  of  the  flutes  is  32 
degrees  at  the  point  of  the  drill  and  27  degrees  at  the  ends  of  the 
flutes  adjacent  to  the  shank,  thus  representing  an  increase  of  7 
degrees  in  each  case,  from  the  angles  which  are  recognized  as 
representative  of  standard  practice. 


DRILLS  AND   DRILL  SOCKETS  107 

Drill  Shanks.  —  Just  as  the  milled  twist  drill  and  the  flat- 
twisted  drill  are  the  two  types  with  which  a  great  majority  of 
drilling  operations  are  performed,  so  the  taper  shank  or  the 
straight  shank  are  the  two  types  of  shanks  that  are  most  com- 
monly used.  At  the  same  time,  there  are  a  number  of  different 
types  of  drill  shanks  which  have  certain  points  of  merit  in  which 
the  reader  will  be  interested.  In  Figs.  2  and  3  are  shown  illus- 
trations of  a  number  of  different  types  of  drill  shanks,  and  the 
advantages  of  these  will  be  very  briefly  discussed.  Starting 
with  the  taper  shank,  the  reader's  attention  is  called  to  the 
fact  that  drills  are  made  in  a  great  variety  of  sizes  to  meet 
the  requirements  of  various  classes  of  work,  but  to  simplify 
the  problems  connected  with  drill  manufacture,  there  is  not 
the  same  diversity  in  the  sizes  of  drill  shanks.  There  are  six 
sizes  of  drill  shanks  with  Morse  tapers  running  from  Nos.  i  to 
6,  inclusive.  The  ranges  of  drill  sizes  for  each  of  these  shanks 
are  shown  in  Table  i. 

Next  to  the  taper  shank,  as  regards  the  extent  to  which  it  is 
used,  comes  the  straight  shank,  and  drills  with  shanks  of  this 
type  are  used  in  various  types  of  drill  chucks.  One  of  the 
chief  claims  made  for  this  type  is  that  its  use  avoids  the  pos- 
sibility of  trouble  through  twisting  off  the  tang  at  the  end  of  a 
taper  shank  drill.  At  C,  Fig.  2,  there  is  shown  what  is  known 
as  the  "  double-grooved  "  or  Graham  shank  which  is  machined 
with  two  parallel  grooves  of  uniform  depth  and  angle.  These 
grooves  correspond  to  the  shape  of  jaws  of  the  chuck  in  which 
the  shank  is  held,  thus  preventing  all  possibility  of  the  shank 
slipping.  With  this  form  of  shank  it  is  possible  to  hold  with 
one  chuck  a  complete  range  of  sizes  of  drills  or  other  tools,  and 
to  tighten  or  release  the  chuck  without  the  use  of  wrenches, 
drifts,  or  other  tools.  A  somewhat  similar  shank  is  shown  at 
D,  this  being  adapted  for  use  in  what  is  known  as  a  "  black- 
smith's "  drill  press.  Here  it  will  be  apparent  that  there  is  a 
flat  milled  on  the  shank  of  the  drill  to  provide  a  positive  drive. 
A  flat- twisted  drill  of  the  type  made  by  the  Celfor  Tool  Co.  is 
shown  at  E  and  this  drill  has  a  shank  particularly  adapted  for 
use  in  connection  with  the  drill  chuck  manufactured  by  this 


io8 


MODERN  DRILLING  PRACTICE 


company.  Used  in  connection  with  the  Celfor  chuck,  this 
type  of  shank  provides  a  positive  drive  and  its  form  is  exception- 
ally well  adapted  to  requirements  which  arise  in  connection  with 
manufacturing  flat-twisted  drills.  A  disadvantage  of  this  type 


K,  M 

Machinery 


Fig.  2.     Drill  Shanks  and  Sockets 

of  shank,  however,  is  that  it  must  be  used  in  connection  with  a 
special  chuck.  At  F  there  is  shown  a  drill  with  a  square  shank 
adapted  for  use  in  a  ratchet.  Both  this  type  of  shank  and  the 
shank  for  blacksmiths'  drills  shown  at  D  are  used  to  a  very 


DRILLS  AND   DRILL  SOCKETS 


109 


slight  extent  in  manufacturing  plants,   their  chief  field  being 
in  the  jobbing  shop  and  on  repair  work,  etc. 

Drill   Sockets.  —  Mention  has  already  been  made  of  the  six 
different  Morse  taper  drill  shanks  that  are  in  general  use.     The 


Machinery 


Fig.  3.     Other  Types  of  Drill  Shanks  and  Sockets 

spindle  of  a  drilling  machine  is  bored  with  a  taper  socket  to  fit 
the  size  of  shank  covering  the  range  of  drill  sizes  which  will  be 
most  generally  used  upon  the  drilling  machine  in  question.  At 
the  same  time,  the  occasion  will  frequently  arise  for  using  a  drill 


no 


MODERN  DRILLING  PRACTICE 


with  a  shank  of  some  size  other  than  the  one  corresponding  to 
the  taper  socket  in  the  drilling  machine  spindle.  To  meet  the 
requirements  of  such  cases,  use  is  made  of  the  familiar  drill 
sockets  which  have  an  inside  taper  hole  corresponding  to  the 
shank  of  the  drill  it  is  required  to  use,  and  a  taper  on  the  out- 
side which  corresponds  to  the  socket  bored  in  the  drilling  ma- 
chine spindle.  Examples  of  such  sockets  are  shown  at  G,  H, 
and  7,  Fig.  2,  these  being  for  what  are  known  as  "  short  "  shank 
drills;  and,  in  addition  to  these  sockets,  most  manufacturers  also 
make  a  series  of  sockets  of  the  same  types,  but  adapted  for 
use  in  connection  with  "  long  "  shank  drills.  The  socket  shown 

Table  i.     Sizes  of  Drills  used  with  Morse  Taper  Shanks 


Morse 
Taper 
Number 

Holds  Drills  Inclusive 
Diameter,  Inches 

Morse 
Taper 
Number 

Holds  Drills  Inclusive 
Diameter,  Inches 

I 

Me  to     gAs 

4 

Il%4    tO   2 

2 

3  £<54   tO      2%2 

5 

2^4     to  3 

3 

5%4   tO   IH 

6 

3^4     to  6 

at  7  is  provided  with  a  shank  which  is  left  rough  so  that  it  may 
be  machined  to  fit  the  spindle  of  the  machine  tool  in  which  the 
socket  will  be  used.  Tables  2  and  3  give  the  ranges  of  combina- 
tions of  inside  and  outside  tapers  in  which  sockets  of  the  types 
shown  at  G  and  H  are  made.  At  /  there  is  shown  a  special 
form  of  split  socket  or  sleeve  which  provides  for  using  a  drill 
with  a  grooved  shank  of  the  form  shown  at  C  in  a  drilling 
machine  equipped  with  the  familiar  Morse  taper  socket  in  the 
spindle.  It  will  at  once  be  apparent  that  the  outside  of  this 
sleeve  is  of  the  usual  taper  shank  form,  while  two  jaws  on  the 
inside  of  the  sleeve  enter  the  grooves  milled  in  the  shank  of 
the  drill. 

For  use  in  connection  with  high-speed  steel  drills  where  a 
strong  positive  drive  is  required,  the  Morse  Twist  Drill  &  Ma- 
chine Co.  makes  sockets  of  the  form  shown  &tK,  Fig.  2,  which 
have  a  clutch  to  engage  a  corresponding  clutch  member  between 
the  taper  shank  and  the  body  of  the  drill  which  is  shown  below 
the  socket  at  KI.  The  drill  shank  has  no  tang;  therefore,  no 


DRILLS   AND   DRILL  SOCKETS 


'III 


dependence  is  placed  upon  this  method  of  driving  and  there  is 
no  danger  of  trouble  from  broken  tangs.  Another  method  oi 
overcoming  trouble  from  this  source  is  shown  in  the  case  of 
drill  shanks  L  and  M,  Fig.  2,  both  of  which  are  adapted  for  use 
in  the  type  of  socket  shown  at  N  and  Ni,  Fig.  3,  drills  and 
sockets  of  this  type  being  made  by  the  Pratt  &  Whitney  Co.  The 
socket  is  of  the  usual  type,  except  that  there  is  a  steel  stud  that 
engages  the  side  of  the  groove  in  the  drill  shank  and  forces  the 
shank  back  into  the  socket.  In  this  way,  the  socket  is  sure  to 
seat  itself  properly,  so  that  the  maximum  friction  drive  is  secured, 
and  this  is  supplemented  by  the  positive  driving  furnished  by  the 

Table  2.     Socket  and  Shank  Combinations 


£=^ 

Socket, 

Shank, 

Socket. 

Shank. 

Socket, 

Shank-, 

Morse 

Morse 

Morse 

Morse 

Morse 

Morse 

Taper  No. 

Taper  No. 

Taper  No. 

Taper  No. 

Taper  No. 

Taper  No. 

2 

I 

3 

2 

5 

3 

Li 

3 
4 

I 

I 

4 
5 

2 
2 

5 

6 

4 

4 

oJ 

5 

I 

4 

3 

6 

5 

steel  stud.  As  no  reliance  is  placed  upon  a  tang  on  the  drill 
shank,  there  is  no  danger  of  the  shank  being  twisted  off  under 
the  most  severe  conditions  of  service  for  which  high-speed  steel 
drills  are  used.  At  0,  Fig.  3,  is  shown  a  drill  socket  made  by  the 
Rich  Tool  Co.,  of  Chicago,  which  is  tapped  to  receive  the 
threaded  end  of  the  drill  shown  at  Oi.  A  socket  which  is  made 
by  the  Morse  Twist  Drill  &  Machine  Co.,  and  known  as  the 
"  Andrews  "  patent  drill  socket,  is  shown  at  P.  This  socket 
is  fitted  with  a  key  sliding  in  a  radial  slot  in  the  holding  head. 
The  key  bears  upon  an  inclined  seat  in  the  shank  of  the  drill 
and  is  forced  to  its  seat  by  a  cap  fitting  over  the  holding  head. 
Turning  this  cap  by  hand  in  one  direction  holds  the  drill  firmly 
in  place,  while  turning  it  in  the  opposite  direction  releases  the 
grip  so  that  the  drill  may  be  readily  removed  from  the  socket. 
Methods  of  Utilizing  Drills  with  Broken  Tangs.  —  While 
going  about  among  machine  shops  in  which  the  management 


112 


MODERN  DRILLING  PRACTICE 


prides  itself  upon  taking  advantage  of  all  possibilities  of  reducing 
production  costs,  it  is  not  uncommon  to  see  a  considerable 
accumulation  of  twist  drills  lying  in  some  corner  of  the  tool- 
room waiting  until  such  a  time  as  they  can  be  disposed  of  for 
their  junk  value.  The  "  business  end "  of  such  drills  will 
often  be  found  in  perfect  condition,  but  they  have  been  dis- 
carded because  the  tang  has  been  twisted  off  the  shank,  making 
it  impossible  to  drive  the  drill  in  the  usual  form  of  socket. 
The  old  saying  that  "  prevention  is  better  than  cure  "  holds 
particularly  true  in  this  case,  and  a  little  care  exercised  by 

Table  3.    Socket  and  Shank  Combinations 


^^ 

S^-  -^ 

Socket, 
Morse 
Taper  No.- 

Shank, 
Morse 
Taper  No. 

Socket, 
Morse 
Taper  No. 

Shank. 
Morse 
Taper  No. 

Socket, 
Morse 
Taper  No. 

Shank, 
Morse 
Taper  No. 

2 

I 

5 

2 

4 

4 

0  , 

3 

I 

2 

3 

5 

4 

—^\ 

4 

I 

3 

3 

6 

4 

5 

I 

4 

3 

4 

5 

r\ 

3 

2 

5 

3 

5 

5 

\\J> 

4 

2 

3 

4 

6 

5 

drilling  machine  operators  would  often  be  the  means  of  saving 
the  twisting  of  tangs  off  many  drills.  Despite  a  somewhat 
general  opinion  to  the  contrary,  the  tang  on  a  taper  shank  is  not 
responsible  for  furnishing  anything  like  the  entire  driving  power. 
Where  a  shank  is  properly  seated  in  its  socket,  friction  between 
the  shank  and  socket  will  exert  a  very  powerful  influence  in 
driving  the  drill.  To  take  advantage  of  this  friction  drive, 
however,  it  is  quite  necessary  for  the  socket  to  be  perfectly 
clean  before  the  drill  shank  is  pushed  into  it.  If  a  small  chip 
is  clinging  to  the  inside  of  the  socket  when  the  drill  shank  is 
pushed  into  place,  this  chip  will  prevent  the  shank  from  coming 
into  contact  with  the  socket  so  that  advantage  may  be  taken  of 
the  friction  drive,  and,  as  a  result,  the  entire  strain  will  come 
upon  the  tang  at  the  end  of  the  shank  with  a  consequent  in- 
crease in  the  probability  that  this  tang  will  be  twisted  off. 


DRILLS   AND   DRILL   SOCKETS  113 

Several  methods  have  been  devised  for  the  utilization  of  drills 
on  which  the  tang  has  been  twisted  off  from  the  shank.  At  Q, 
Fig.  3,  there  is  shown  a  socket  corresponding  to  the  usual  type 
of  socket,  except  that  it  is  split.  Even  where  the  tang  has 
been  twisted  off  a  drill,  a  socket  of  this  kind  will  provide  a 
sufficiently  tight  grip  on  the  drill  shank  to  afford  the  necessary 
driving  power.  At  R  is  shown  what  is  known  as  a  "  tang  gage." 
Where  the  tang  has  been  twisted  off  a  drill  shank,  this  gage  is 
used  to  mark  the  outline  of  a  new  tang  after  which  the  shank  is 
ground  down  to  the  outline  laid  out  with  this  gage,  so  that  the 
drill  can  once  more  be  driven  in  the  usual  manner.  The  "  wear- 
ever  "  drill  socket  shown  at  S  is  made  by  Scully- Jones  &  Co. 
It  has  a  flat  on  the  inside  of  the  socket  to  drive  drills  from  which 
the  tang  has  been  twisted  off,  a  corresponding  flat  being  ground 
on  the  shank  of  the  drill  to  engage  this  flat  in  the  socket.  The 
flange  at  the  bottom  of  this  socket  furnishes  additional  strength 
and  prevents  the  socket  from  spreading.  The  "  use-em-up  " 
drill  socket  shown  at  T  is  made  by  the  American  Specialty  Co., 
and  reference  to  this  socket  will  make  it  apparent  that  pro- 
vision is  made  for  using  a  drill  with  a  broken  tang  by  simply 
grinding  a  flat  on  the  side  of  the  drill  shank.  The  socket  shown 
at  U  has  nothing  to  do  with  the  utilization  of  drills  on  which 
the  tang  has  been  twisted  off  from  the  shank.  This  type  of 
socket  is  for  use  in  connection  with  oil  tube  drills.  The  collar 
on  the  socket  is  held  stationary  by  the  supply  pipe  that  connects 
with  a  nipple  through  which  oil  is  delivered  to  the  tubes  in  the 
drill  that  carry  it  direct  to  the  cutting  point. 


CHAPTER  VI 
TYPES   OF   COMMONLY  USED   DRILL   CHUCKS 

THERE  are  three  general  methods  of  holding  drills  in  the 
spindles  of  drilling  machines  and  other  machine  tools.  These 
are  as  follows:  i.  By  inserting  the  drill  shank  directly  into  a 
hole  in  the  machine  spindle.  2.  By  inserting  the  drill  shank 
in  a  socket  or  sleeve  which  fits  into  the  drill  spindle.  3.  By  us- 
ing some  form  of  drill  chuck.  Although  there  are  one  or  two 
types  of  drill  chucks  adapted  for  holding  drills  with  the  familiar 
form  of  tapered  shank,  by  far  the  more  general  practice  is  to 
use  drills  with  straight  shanks  in  all  cases  where  drill  chucks  are 
to  be  employed.  Drill  chucks  are  made  in  a  variety  of  different 
designs,  all  of  which  are  claimed  to  possess  certain  valuable 
features  which  adapt  them  for  securely  holding  drills  without 
marring  the  shanks  and  various  other  advantages.  All  drill 
chucks  are  provided  with  sufficient  adjustment  to  adapt  them 
for  holding  different  sizes  of  drill  shanks,  and  it  is  this  capacity 
for  handling  a  range  of  sizes,  together  with  ability  to  secure  a 
firm  driving  grip  on  the  drill  without  marring  the  shank,  and  the 
possibility  of  rapidly  changing  from  one  size  of  drill  to  another, 
which  are  the  chief  advantages  secured  through  the  use  of  drill 
chucks  over  other  methods  of  mounting  drills  in  the  spindles  of 
drilling  machines. 

All  types  of  drill  chucks  may  be  roughly  subdivided  into  two 
general  classes;  namely,  those  types  in  which  opening  and 
closing  of  the  jaws  is  controlled  through  the  action  of  a  geared 
sleeve,  a  screw,  or  some  similar  method;  and  the  so-called 
"  quick-acting  "  or  "  automatic  "  chucks,  in  which  provision  is 
made  for  rapidly  operating  the  chuck  jaws  by  hand,  without 
requiring  the  use  of  a  wrench  or  other  tool,  so  that  the  tools  may 
be  rapidly  changed  in  cases  where  a  sequence  of  drilling,  counter- 
boring,  and  reaming  operations,  etc.,  have  to  be  performed.  In 

114 


DRILL  CHUCKS  115 

the  following  paragraphs,  a  brief  description  will  be  given  of  a 
number  of  types  of  drill  chucks  that  find  quite  general  appli- 
cation in  American  machine  shops. 

Use  of  Quick-change  Collet  Chucks.  —  Where  there  is  a 
sequence  of  machining  operations  to  be  performed,  for  in- 
stance where  it  is  necessary  to  drill,  counterbore,  and  tap  a 
hole,  the  planning  department  which  decides  the  methods  of 
performing  machining  operations  has  a  choice  between  the  use 
of  a  straight-line  multiple-spindle  drilling  machine  or  a  single- 
spindle  machine  equipped  with  a  quick-change  chuck.  The 
use  of  multiple-spindle  machines  has  been  discussed  in  another 
section  of  this  book  and  we  are  now  concerned  with  the  method 
of  handling  the  work  on  a  single-spindle  machine.  Quick- 
change  chucks  may  be  of  the  so-called  "  automatic  "  type,  in 
which  one  tool  may  be  instantly  released  from  the  chuck  and 
another  substituted,  or  they  may  be  of  the  quick-change  collet 
type,  four  examples  of  which  are  illustrated  in  Fig.  i.  The 
difference  between  the  automatic  chuck  and  the  collet  chuck 
is  that  the  former  grips  directly  upon  the  shank  of  the  drill, 
while  the  latter,  as  its  name  implies,  grips  a  special  collet  in 
which  the  drill  is  held.  The  advantage  of  either  type  of  chuck 
for  use  in  performing  a  sequence  of  operations  on  a  single- 
spindle  machine  is  that  practically  no  time  is  lost  in  changing 
tools.  Not  only  are  both  the  automatic  and  collet  types  of 
chucks  rapid  to  operate,  but  they  are  so  designed  that  it  is 
unnecessary  to  stop  the  spindle  of  the  machine  in  order  to 
change  tools. 

At  A,  in  Fig.  i,  is  shown  the  "magic  "  chuck  made  by  the 
Modern  Tool  Co.  This  chuck  consists  of  a  cylindrical  body 
with  a  taper  shank  and  two  steel  balls  that  move  in  and  out  of 
races  milled  through  the  chuck  body  so  that  they  can  enter 
corresponding  races  in  the  locking  ring  which  is  mounted  loosely 
on  the  chuck  body.  The  body  is  bored  out  in  the  center  to 
receive  collets  in  which  various  types  of  tools  are  carried. 
These  collets  are  made  of  tool  steel  with  ball  races  to  receive 
the  balls  carried  in  the  chuck  body,  the  way  in  which  the  collet 
is  held  in  place  in  the  body  of  the  chuck  being  shown  by  dotted 


n6 


MODERN  DRILLING  PRACTICE 


lines.  When  the  locking  ring  is  raised,  centrifugal  force  pushes 
the  balls  out  into  the  races  cut  in  the  locking  ring,  leaving  a 
perfectly  clear  opening  for  the  collet;  and  when  the  ring  is 
released  gravity  draws  it  down,  thus  forcing  the  balls  back 
through  the  walls  of  the  chuck  so  that  they  enter  the  slots  or 
races  in  the  collet  to  hold  it  in  place.  Thus  two  natural  forces 
are  utilized  to  secure  a  quick  release  and  positive  grip.  The 
body  of  the  chuck  is  made  of  crucible  steel  and  the  collet  of  tool 
steel  with  the  races  hardened  to  provide  the  required  durability. 


A     A 


Fig.  i.     Quick-change  Collet  Chucks 

By  using  a  special  type  of  split  collet  in  connection  with  one  of 
the  collets  adapted  for  use  in  this  chuck,  it  is  possible  to  use 
taper  shank  drills  from  which  the  tangs  have  been  twisted  off. 
These  chucks  are  made  with  Morse  taper  shanks  from  Nos.  i 
to  6,  inclusive,  and  collets  for  use  in  the  chucks  are  made  with 
sockets  to  fit  Nos.  i  to  5  Morse  taper  shanks,  inclusive;  special 
collets  are  also  made  to  meet  the  requirements  of  other  tools. 
At  £,  Fig.  i,  there  is  illustrated  the  "Presto"  drill  chuck 
that  is  made  by  the  Whitney  Mfg.  Co.  Chucks  of  this  type 
are  furnished  with  shanks  fitted  to  Nos.  2,  3,  and  4  Morse  taper 
sockets  or  with  the  shanks  left  blank,  and  collets  are  made  to 
fit  tools  with  Nos.  1,2,  and  3  Morse  taper  shanks;  collets  may 


DRILL  CHUCKS  117 

also  be  furnished  blank  so  that  they  may  be  machined  to  meet 
special  requirements.  To  operate  this  collet  chuck,  it  is  merely 
necessary  to  lift  the  releasing  ring  which  allows  the  collet  in  the 
chuck  to  be  instantly  removed  and  another  collet  carrying  the 
next  tool  to  be  substituted  in  its  place.  The  collet  is  driven 
by  a  tang  entering  a  socket  in  the  chuck.  Dropping  the  ring 
locks  the  new  collet  in  place. 

At  C,  Fig.  i,  there  is  shown  a  drill  chuck  made  by  the  Quick 
Action  Chuck  Co.,  which  is  made  in  three  different  sizes  with 
shanks  ranging  from  Nos.  i  to  6  Morse  taper,  inclusive.  Collets 
are  made  for  use  in  this  chuck  which  have  a  capacity  for  Morse 


JAWS  OPENED  JAWS  CLOSED 

Machinery 


Fig.  2.     Chuck  having  Eccentric  Rollers  which  Grip  Drill  Shank 

taper  shank  drills  from  Nos.  i  to  5,  inclusive,  and  special  collets 
are  made  to  hold  tools  with  any  size  of  shank  up  to  i|  inch  in 
diameter.  The  collet  in  the  chuck  is  released  by  simply  raising 
the  sliding  sleeve  and,  after  a  fresh  tool  has  been  substituted, 
dropping  the  sleeve  locks  the  collet  carrying  this  tool  firmly  in 
the  chuck. 

The  Wiard  chuck  shown  at  D,  Fig.  i,  is  made  by  the  Eclipse 
Interchangeable  Counterbore  Co.  These  chucks  are  made  in 
five  different  sizes  with  shanks  ranging  from  Nos.  i  to  5  Morse 
taper,  inclusive.  The  different  sizes  of  chucks  are  adapted  for 
drills  up  to  -ft,  |~|,  f  |,  ij,  and  2  inches  in  diameter,  respectively. 
The  way  in  which  this  chuck  operates  will  be  apparent  after 
referring  to  the  illustration.  Lifting  the  loose  sleeve  that  sur- 
rounds the  body  of  the  chuck  brings  a  groove  in  this  sleeve  into 
line  with  the  corresponding  groove  in  the  chuck  body.  In  this 
position,  the  steel  disks  which  lock  the  collet  in  place  in  the 


n8 


MODERN  DRILLING  PRACTICE 


chuck  are  allowed  to  roll  back  so  that  one  collet  may  be  with- 
drawn and  another  collet  pushed  up  into  place  in  the  chuck. 
After  this  has  been  done,  the  sleeve  is  dropped,  thus  forcing  the 
steel  disks  back  so  that  they  engage  the  collet  and  lock  it  firmly 
in  place  in  the  chuck.  It  will,  of  course,  be  apparent  that,  in 
the  case  of  the  chucks  shown  at  A ,  B,  C,  and  D,  it  is  unnecessary 
to  stop  the  machine  while  changing  tools,  because  the  sleeve  or 
ring  that  operates  the  chuck  may  be  held  while  the  spindle 
rotates. 

Automatic  Drill  Chucks.  —  Figs.   2   and  3   show  two  well- 
known  types  of  quick-acting  or  automatic  drill  chucks  which 

are  operated  by  hand,  making 
chucks  of  these  types  well  adapted 
for  use  on  drilling  machines  where 
it  is  required  to  perform  a  se- 
quence of  operations  making 
necessary  the  frequent  changing 
of  tools.  In  the  chuck  shown 
in  Fig.  2,  which  is  made  by  the 
Wahlstrom  Tool  Co.,  the  drill 
shank  is  gripped  by  three  eccen- 
tric rollers  A,  which  are  so  de- 
signed that,  when  in  contact  with 
the  shank  of  the  drill,  the  resistance  offered  by  the  drill  to  being 
driven  into  the  work  causes  these  rollers  A  to  rock  in  such  a  way 
that  they  close  in  toward  a  common  center  and  thus  grip  the 
drill  shank,  due  to  the  eccentric  form  of  the  rollers.  Owing 
to  the  way  in  which  this  chuck  operates,  the  amount  of  grip- 
ping power  applied  by  the  chuck  is  in  direct  proportion  to  the 
resistance  offered  by  the  drill  to  being  driven  into  the  work. 
In  other  words,  the  power  applied  by  the  chuck  is  in  direct 
proportion  to  the  service  required  of  it.  Adjustment  of  the 
chuck  for  holding  drills  with  shanks  of  various  sizes  is  afforded 
by  means  of  three  cam  surfaces  B  on  the  inside  of  the  chuck  shell. 
To  open  the  chuck,  the  drilling  machine  operator  grips  the 
knurled  surface  on  the  outside  of  the  chuck  shell  and  holds  this 
shell  back  against  the  rotation  of  the  drilling  machine  spindle, 


MacMnery 


Fig.  3. 


Chuck  equipped  with  Cams 
and  Rollers 


DRILL   CHUCKS 


thus  causing  the  chuck  jaws  to  recede  to  their  position  of  widest 
opening.  The  drill  in  the  chuck  then  drops  out  and  the  machine 
operator  simply  pushes  the  next  drill  to  be  used  up  into  the  chuck 
and  releases  the  shell,  so  that  a  spring  in  the  chuck  may  rotate  this 
shell  sufficiently  to  cause  cam  surfaces  B  to  bring  eccentric  jaws 
A  into  contact  with  the  drill  shank.  The  grip  provided  by  the 
jaws  through  this  spring  action  is  sufficient  to  hold  the  drill  in 
place  in  the  chuck,  but  would  not  be  sufficient  to  drive  the  drill 
when  in  contact  with  the  work.  When  the  machine  spindle  is 
fed  downward  so  that  the  drill  engages  the  work,  the  resistance 


Machinery 


Fig.  4.     Drill  Chucks  of  the  Screw  Type 

offered  by  the  drill  to  being  driven  causes  eccentric  jaws  A  to 
rock  and  secure  a  grip  on  the  drill  shank  in  the  manner  to  which 
reference  has  already  been  made. 

In  the  Gronkvist  automatic  drill  chuck  (SKF  Ball  Bearing 
Co.,  Hartford,  Conn.)  shown  in  Fig.  3,  the  method  of  operating 
the  chuck  and  providing  for  securing  a  grip  on  the  drill  shank  by 
the  chuck  jaws  is  somewhat  similar  to  that  of  the  chuck  shown  in 
the  preceding  illustration.  Here  it  will  be  seen  that  the  jaws  A 
are  cylindrical  in  form  and  three  cam  surfaces  B  provide  for 
adjusting  the  position  of  these  jaws  for  holding  drills  of  different 
sizes .  The  chuck  is  operated  by  holding  the  knurled  shell  or  slee v e 


120 


MODERN  DRILLING  PRACTICE 


back  against  the  direction  of  rotation  of  the  drilling  machine 
spindle  and,  when  jaws  A  secure  a  preliminary  grip,  the  required 
grip  for  driving  is  secured  through  resistance  offered  by  the  drill 
against  rotation  causing  the  jaws  A  to  roll  sufficiently  on  cam 
surfaces  B,  so  that  the  jaws  are  forced  in  against  the  drill  shank. 
Two-jaw  Screw-type  Drill  Chuck.  —  There  are  a  number  of 
concerns  making  drill  chucks  of  the  general  type  shown  in  Fig.  4, 
which  are  furnished  with  two  jaws  operated  by  a  screw  and 
hand  wrench.  The  chuck  shown  at  A  in  this  illustration  is 
made  by  the  Cushman  Chuck  Co.  In  these  chucks,  the  jaws 


Machinery 


Fig.  5.     Chucks  of  the  Geared  Type 

are  threaded  at  the  side  to  engage  an  operating  screw  which  is 
threaded  right  hand  at  one  end  and  left  hand  at  the  opposite 
end,  so  that  turning  of  this  operating  screw  with  a  hand  wrench 
provides  for  tightening  or  loosening  the  two  jaws  simultaneously. 
The  type  of  chuck  shown  at  B  is  made  by  the  Westcott  Chuck 
Co.,  and  the  feature  of  its  design  consists  of  the  provision  of  an 
auxiliary  screw  a  that  engages  threaded  sections  of  the  chuck 
jaws  at  the  opposite  side  from  the  main  operating  screw  b,  thus 
avoiding  all  tendency  for  the  jaws  to  crowd  away  from  the  right- 
and  left-hand  sections  of  the  operating  screw.  At  C,  there  is 
shown  a  chuck  made  by  the  Pratt  Chuck  Co.,  in  which  the  ar- 
rangement of  jaws  and  method  of  operation  is  the  same  as  that 


DRILL  CHUCKS 


121 


of  the  chuck  shown  at  A .  The  feature  of  this  chuck  consists  of 
an  equalizing  driver  c  which  is  slotted  to  receive  the  drill  tang  d, 
thus  providing  a  positive  drive  which  is  independent  of  the  grip 
on  the  drill  shank  afforded  by  the  chuck  jaws.  This  driver  is 
self-adjusting,  permitting  the  jaws  to  center  and  line  up  the 
drill  accurately  in  the  chuck. 

Geared  Type  of  Chuck.  —  The  chuck  shown  at  A,  in  Fig.  5, 
is  made  by  the  Jacobs  Mfg.  Co.,  and  tightening  of  the  jaws 
is  accomplished  in  the  following  manner :  A  hand  wrench  carry- 


WacMnery 


Fig.  6.    Another  Chuck  of  the  Geared  Type 

ing  pinion  a  is  piloted  to  fit  into  bushings  in  the  chuck  body, 
and  this  pinion  a  meshes  with  gear  teeth  b  cut  in  the  bottom  of  a 
sleeve  of  which  threaded  ring  c  is  an  integral  part.  This 
threaded  ring  meshes  with  threads  cut  in  the  upper  outside 
portion  of  each  of  the  three  chuck  jaws  d.  Evidently,  when 
the  wrench  is  turned,  pinion  a  turns  sleeve  b  and  threaded  ring 
c,  which  is  an  integral  part  of  the  sleeve,  thus  either  pushing 
down  or  lifting  chuck  jaws  d  according  to  the  direction  in  which 
the  wrench  is  turned.  By  having  jaws  d  inclined  to  the  axis  of 
the  drill,  raising  or  lowering  the  jaws  causes  them  to  release 
their  grip  on  the  drill  shank  or  to  secure  a  firm  grip. 


122 


MODERN  DRILLING  PRACTICE 


At  B,  Fig.  5,  there  is  shown  a  chuck  operating  on  the  same 
general  principle,  which  is  made  by  the  J.  R.  Almond  Mfg.  Co. 
This  illustration  shows  the  outside  of  the  chuck  with  the  operat- 
ing wrench  in  position,  and  in  connection  with  the  cross-sectional 
view  of  the  Jacobs  chuck  shown  at  A  it  gives  a  very  clear  idea 
of  the  design  and  operation  of  this  type  of  geared  chuck.  The 
chuck  shown  in  Fig.  6,  made  by  the  Skinner  Chuck  Co.,  is  so 
designed  that  it  may  be  operated  by  hand  except  for  obtaining 
the  final  grip  of  the  jaws  on  the  drill  shank  or  for  releasing  these 


Machinery 


Fig.  7.     Chucks  of  the  Knurled-sleeve  Type 

jaws  after  the  drill  has  been  in  operation,  a  wrench  being  em- 
ployed for  this  purpose  which  fits  in  the  square  hole  in  either 
of  the  pinions  A  which  mesh  with  a  gear  B  that  governs  the 
operation  of  the  chuck  jaws.  This  feature  of  hand  adjustment 
is  also  common  to  the  chucks  shown  in  Fig.  5. 

Wrenchless  Drill  Chucks.  —  In  some  shops,  an  objection  is 
made  to  the  use  of  chucks  which  are  operated  by  a  wrench, 
because  it  is  claimed  that  trouble  is  often  experienced  through 
having  the  wrench  mislaid.  The  exponents  of  this  theory 
have  developed  hand-operated  drill  chucks  which  are  made 
with  a  knurled  sleeve  that  may  be  gripped  by  hand  and  turned 
in  either  direction  in  order  to  tighten  or  loosen  the  grip  of  the 


DRILL  CHUCKS 


123 


jaws  on  the  drill  shank.  The  chuck  shown  at  A  in  Fig.  7 
is  made  by  E.  Horton  &  Son  Co.  This  chuck  is  furnished 
with  ball  bearings  so  that  its  operation  is  made  as  easy  as 
possible.  A  coarse  pitch  screw  provides  quick  adjustment  of 
the  chuck  jaws,  while  a  fine  pitch  screw  tightens  up  the  jaws 
to  afford  the  desired  driving  grip  on  the  drill  shank.  At  B, 
there  is  shown  a  drill  chuck  made  by  the  Nielsen-Barton  Chuck 
Co.,  and  the  chuck  shown  at  C  is  a  product  of  the  Goodell  Pratt 
Co.  Both  of  these  chucks  are  hand  operated,  so  that  they  pro- 


Slachlnery 


Fig.  8.     Chucks  for  Drills  having  Shanks  of  Special  Form 

vide  for  quickly  changing  the  tools  and  also  avoid  any  possible 
complications  through  loss  of  the  operating  wrench. 

Chucks  for  Special  Drill  Shanks. — The  preceding  types  of  drill 
chucks  are  universal  in  their  scope,  being  adapted  for  driving 
any  standard  straight  shank  drill  which  comes  within  their  range. 
Reference  to  Figs.  2  and  3,  Chapter  V,  will  show  that  there  are  a 
number  of  special  forms  of  drill  shanks,  and  for  driving  drills 
with  such  shanks,  the  drill  chucks  must  be  especially  designed 
for  the  purpose.  For  instance,  at  C,  Fig.  2,  there  is  shown  what 
is  known  as  the  Graham  grooved  shank,  drills  of  this  type  being 
made  by  the  National  Twist  Drill  &  Tool  Co.  and  also  by  the 


124  MODERN  DRILLING  PRACTICE 

Detroit  Twist  Drill  Co.  To  provide  for  holding  drills  with  this 
type  of  shank,  both  of  these  firms  make  chucks  with  a  special 
form  of  jaw  adapted  to  fit  into  the  groove  in  the  drill  shanks. 
At  A,  in  Fig.  8,  there  is  shown  one  of  these  chucks  which  is  a 
product  of  the  Detroit  Twist  Drill  Co.  It  will  be  evident  from 
this  illustration  that  when  sleeve  a,  which  is  threaded  internally 
to  fit  over  the  threaded  section  b  of  the  chuck  body,  is  screwed 
up,  the'  taper  on  the  inside  of  sleeve  a,  that  engages  a  corre- 
sponding taper  on  jaws  c,  causes  these  jaws  to  be  sprung  in- 
ward to  grip  the  grooves  in  the  drill  shank.  At  E  in  Fig.  2  (Chap- 
ter V)  there  is  shown  the  type  of  shank  provided  on  the  flat- 
twisted  drills  made  by  the  Celfor  Tool  Co.,  and  to  meet  the 
requirements  of  holding  drills  with  shanks  of  this  type,  this 
firm  makes  a  special  drill  chuck  as  shown  at  B  in  Fig.  8.  This 
chuck  is  provided  with  jaws  which  are  grooved  to  receive  the 
central  beads  on  the  drill  shank.  It  will  be  apparent  that  the 
chuck  is  an  extremely  simple  design  and  is  strongly  constructed 
to  stand  up  under  severe  service.  The  Celfor  drill  shanks  are 
made  with  the  four  corners  of  the  shank  beveled  so  that  they 
are  accurately  located  at  an  equal  distance  from  the  center 
line  of  the  drill.  At  C,  Fig.  8,  there  is  shown  a  type  of  drill 
chuck  which  is  designed  to  take  advantage  of  this  beveling  of  the 
corners  of  the  Celfor  drill  shank  by  holding  drills  of  this  type 
by  the  beveled  corners. 

The  Rich  Tool  Co.  makes  a  type  of  drill  in  which  the  two 
spiral  grooves  of  the  drill  are  continued  to  the  end  of  the  drill 
shank,  although  these  grooves  change  their  direction  to  run 
parallel  to  the  axis  of  the  drill  over  the  entire  length  of  the  shank. 
To  provide  for  driving  drills  of  this  type,  the  Rich  Tool  Co. 
makes  a  drill  chuck  shown  at  D  in  Fig.  8.  This  chuck  is  simply 
constructed,  consisting  of  only  four  parts;  namely,  the  body  d, 
operating  nut  e,  and  two  jaws  /.  This  chuck  may  be  quickly 
adjusted  and  is  said  to  be  well  suited  for  use  where  frequent 
changes  of  tools  must  be  made.  The  jaws  /  clamp  an  inward 
taper  in  the  grooves  on  the  drill  shank,  which  prevents  the  drill 
from  being  pulled  out  even  where  the  grip  of  the  jaws  on  the 
drill  shank  has  not  been  made  sufficiently  tight. 


CHAPTER  VII 
DRILL   GRINDING 

IN  order  to  give  satisfactory  service,  a  drill  must  be  ground 
so  that  its  point  is  of  the  correct  form.  Efficient  results  can- 
not be  expected  from  a  drill  in  which  the  material  and  original 
workmanship  are  of  the  required  standard,  unless  the  subse- 
quent work  of  grinding  to  keep  the  point  of  the  drill  in  working 
condition  is  handled  in  such  a  way  that  the  proper  form  is 
maintained.  It  is  very  difficult  to  grind  a  drill  by  hand  and 
secure  the  desired  results  without  spending  too  much  time  on  the 
work.  Men  employed  in  factories  manufacturing  drills  learn  to 
do  this  work  very  rapidly  as  the  result  of  their  special  experience, 
but  the  drilling  machine  operator  or  tool-room  attendant  who 
attempts  to  grind  a  drill  by  hand  is  likely  to  fail  to  produce  a 
point  which  comes  even  reasonably  near  to  meeting  all  require- 
ments. It  is  generally  conceded  that  the  form  of  a  drill  point 
exerts  a  powerful  influence  upon  the  rate  of  production,  accuracy 
of  drilled  holes,  and  the  number  of  holes  which  can  be  drilled 
between  successive  grindings.  Granting  this  to  be  the  case,  it 
at  once  becomes  apparent  that  steps  should  be  taken  to  provide 
for  grinding  drills  in  such  a  way  as  to  enable  them  to  give  the 
maximum  amount  of  service. 

Requirements  in  Drill  Grinding.  —  For  the  average  shop,  the 
only  way  to  be  sure  of  attaining  such  a  result  is  to  have  the  drills 
ground  on  special  drill  grinding  machines  which  are  so  designed 
that  they  assure  producing  drill  points  that  meet  all  requirements. 
These  requirements  are  as  follows:  (i)  Both  cutting  lips  of  a 
drill  must  be  inclined  at  the  same  angle  with  the  axis  of  the  drill. 
(2)  Both  cutting  lips  must  be  of  exactly  the  same  length.  (3) 
The  drill  point  must  have  the  proper  lip  clearance  or  contour  of 
the  surface  back  of  the  cutting  edges,  and  this  clearance  must 
be  the  same  for  each  side  of  the  drill.  All  of  these  factors  are  of 
the  utmost  importance  in  enabling  a  drill  to  give  satisfactory 

125 


126 


MODERN  DRILLING  PRACTICE 


service.  The  various  undesirable  conditions  which  it  is  possible 
to  produce  through  improper  drill  grinding  are  shown  in  Fig.  i. 
If  both  lips  of  the  drill  are  not  inclined  at  the  same  angle  a 
with  the  axis,  one  lip  will  fail  to  counteract  the  tendency  of  the 
other  to  spring  away  from  the  cut.  Furthermore,  this  will  re- 
sult in  having  one  lip  of  the  drill  do  more  wrork  than  the  other, 
with  the  result  that  this  lip  will  soon  become  dull,  and  an  abnor- 
mal torsional  strain  will  also  be  set  up.  When  the  cutting  lips 
of  the  drill  have  the  same  inclination  to  the  axis  but  are  of 
different  lengths,  it  means  that  the  point  of  the  drill  is  off  center, 
and  as  a  result  the  hole  will  be  cut  over  size  by  an  amount  equal 
to  twice  the  eccentricity  of  the  drill  point.  It  is  also  possible 


A  LIPS  OF  DIFFERENT 
INCLINATIONS 


B    LIPS  OF  DIFFERENT 
LENGTHS 


C  LIPS  WITH  DIFFERENT  INCLINATIONS 
AND  DIFFERENT  LENGTHS 

Machinery 


Fig.  i. 


Conditions  under  which  a  Twist  Drill  may  be  forced  to 
Operate  through  Incorrect  Drill  Grinding 


to  have  an  error  in  both  the  angle  of  drill  point  and  equality 
of  length  of  the  lips  of  the  drill,  and  where  such  a  condition 
exists  there  will  be  a  combination  of  the  undesirable  results 
which  have  been  mentioned. 

Concerning  Angles  of  Drill  Points.  —  An  angle  of  59  degrees 
has  been  adopted  as  the  standard  angle  for  the  points  of  twist 
drills,  and  such  a  point  is  well  suited  for  drills  engaged  on  all 
average  classes  of  work.  There  are  certain  cases,  however, 
where  a  modification  of  the  form  of  the  drill  point  is  considered 
advisable.  For  instance,  where  a  drill  is  fed  down  onto  the 
surface  of  a  piece  of  work  held  at  an  angle  to  it,  and  where  no 
guide  bushing  is  provided  to  hold  the  drill  in  the  desired  position, 
it  will  be  found  desirable  to  make  the  drill  point  to  an  angle 
more  acute  than  59  degrees  in  order  to  facilitate  penetration  of 


DRILL   GRINDING  127 

the  drill  point  without  tendency  for  it  to  slide  down  on  the  surface 
of  the  work.  Conversely,  a  drill  which  is  used  to  make  holes  in 
fairly  thin  tubing  will  give  better  results  where  the  point  is 
made  blunter  than  that  of  a  standard  drill.  The  reason  for  this 
is  that  the  feed  pressure  of  the  drill  tends  to  spring  the  tubing 
slightly  until  the  point  of  the  drill  starts  to  break  through;  then 
the  work  springs  back  quickly  to  its  original  position  and  in- 
creases the  rate  of  feed  —  the  condition  being  similar  to  that 
explained  in  connection  with  Fig.  7,  which  shows  the  result 
of  spring  in  the  members  of  a  drilling  machine  —  and  such  a 
condition  may  cause  the  drill  to  be  broken. 

The  two  conditions  which  have  been  cited  are  typical  of 
instances  where  it  is  necessary  to  reduce  the  standard  angle 
when  grinding  drills.  In  general,  if  there  is  marked  trouble 
through  breakage  of  drills,  and  the  other  conditions  which 
are  likely  to  result  in  breakage  are  considered  satisfactory, 
a  slight  modification  of  the  drill  point  may  produce  a  drill 
which  gives  the  desired  results  without  trouble  from  breaking. 
Another  case  where  it  is  necessary  to  modify  the  standard 
form  of  twist  drills  is  when  drills  are  used  for  cutting  brass. 
Here  the  standard  angle  of  rake  provided  for  use  in  drilling 
iron  or  steel  is  such  that  the  drill  would  tend  to  hog  into  the 
work  and  produce  an  unsatisfactory  condition  of  operation. 
To  overcome  this  difficulty,  it  is  the  practice  to  grind  the  drill 
so  that  the  rake  angle  is  reduced  practically  to  zero.  Drills 
ground  in  this  way  will  cut  quite  freely  and  give  a  satisfactory 
rate  of  production. 

Clearance  behind  Cutting  Edges.  —  In  order  that  a  drill  may 
cut  properly,  there  must  be  the  correct  amount  of  clearance 
behind  each  of  the  cutting  edges  so  that  these  edges  may  be 
forced  down  into  the  work.  Where  there  is  insufficient  clearance, 
a  drill  will  not  cut  freely;  and  too  much  clearance  results  in 
weakening  the  tool  at  its  cutting  edges.  Theoretically,  the 
amount  of  clearance  should  be  slightly  in  excess  of  that  which 
is  actually  required  for  the  rate  of  feed  under  which  the  drill  is 
being  operated,  because  any  excess  clearance  results  in  a  corre- 
sponding weakening  of  the  cutting  edge  of  the  drill.  As  a 


128  MODERN  DRILLING  PRACTICE 

matter  of  fact,  drills  are  usually  ground  with  an  amount  of 
clearance  sufficient  to  take  care  of  the  maximum  feed  under 
which  they  are  likely  to  be  operated,  and  when  so  ground  the 
amount  that  the  cutting  edges  are  weakened  can  safely  be 
disregarded.  In  order  to  clearly  understand  the  conditions 
which  must  be  fulfilled  in  order  to  grind  the  desired  amount  of 
clearance  on  the  point  of  a  drill,  it  is  necessary  first  to  appreciate 
the  fact  that  every  point  (as  at  A  and  B,  Fig.  2)  on  each  cutting 
edge  is  advanced  on  a  spiral  path  as  the  drill  is  fed  into  the  work. 
All  of  these  spiral  paths  have  the  same  lead  x  —  which  is  equal 


Machinery 


Fig.  2.     Diagram  showing  why  Clearance  Angle  should  Increase 
Toward  the  Drill  Point 

to  the  rate  of  feed  per  revolution  —  but  each  spiral  has  a  differ- 
ent diameter. 

The  clearance  angle  i?  defined  as  the  angle  which  a  tangent 
to  the  spiral  path  followed  by  a  point  on  the  cutting  edge  at 
the  periphery  of  the  drill  makes  with  the  axis  of  the  drill.  This 
fact  in  regard  to  each  point  following  its  own  spiral  path  will 
be  readily  understood  by  referring  to  Fig.  2.  A  study  of  this 
illustration  will  also  show  the  requirements  which  must  be 
fulfilled  in  order  to  grind  the  proper  clearance  on  the  point  of  a 
drill.  It  will  be  apparent  that  the  clearance  must  increase  from 
the  periphery  of  the  drill  to  the  center.  This  is  due  to  the  fact 
that,  while  the  spirals  at  all  points  along  the  lip  of  the  drill  have  the 


DRILL  GRINDING 


129 


same  lead,  the  diameter  of  each  spiral  is  constantly  growing  less 
as  it  passes  from  the  periphery  of  the  drill  to  the  center.  Con- 
sequently point  B  follows  a  steeper  path  than  A  which  accounts 
for  the  increase  in  the  clearance  angle  from  the  periphery  toward 
the  center.  In  drills  made  by  the  Cleveland  Twist  Drill  Co., 
the  clearance  angle  at  the  periphery  is  from  12  to  15  degrees, 
and  this  angle  increases  uniformly  from  the  periphery  to  the 
center  in  such  a  way  that  the  angle  made  by  the  chisel  point 
with  each  cutting  edge  of  the  drill  is  from  125  to  135  degrees. 
This  is  the  condition  indicated  in  Fig.  3. 


•Machinery 


Fig.  3.     Commercial  Standards  for  Angle  of  Drill  Point,  Clearance, 
and  Angle  made  by  Chisel  Point  with  Cutting  Edges  of  Drill 

In  order  to  regulate  the  clearance  so  that  it  is  correct  for 
each  lip  of  the  drill  all  of  the  way  from  the  periphery  to  the 
center,  and  to  relieve  each  surface  back  of  the  cutting  edges 
so  that  the  proper  degree  of  endurance  and  strength  will  be 
secured,  it  is  necessary  for  the  point  of  the  drill  to  rock  against 
the  grinding  wheel  while  it  is  being  ground  in  a  path  similar  to 
that  which  it  follows  while  actually  being  fed  into  a  piece  of 
work.  In  order  to  secure  this  result,  it  is  necessary  to  maintain 
the  desired  relation  between  the  angle  at  which  the  drill  is  held 
against  the  grinding  wheel  and  the  axis  about  which  it  is  rocked 
while  in  contact  with  the  wheel. 


MODERN  DRILLING  PRACTICE 


In  Fig.  4,  let  AB  in  each  diagram  represent  the  axis  about 
which  the  drill  is  rocked  while  being  ground,  and  let  C  and  D 
represent  the  radii  of  arcs  through  which  different  portions  of 
the  drill  lip  will  be  swung  during  the  grinding  operation.  In 


Machinery 


Fig.  4.  Diagrams  showing  Correct  and  Incorrect  Relations  between 
Face  of  Grinding  Wheel  and  Axis  about  which  Drill  is  rocked 
while  being  ground 

order  to  have  the  clearance  increase  from  the  periphery  of  the 
drill  to  the  center,  it  is  obvious  that  those  portions  near  the 
center  must  travel  on  shorter  paths  and  smaller  circles  than 
portions  near  the  outer  corner  of  the  lip.  In  other  words,  radius 
C  must  be  shorter  than  radius  D  in  order  to  secure  the  desired 
clearance.  In  the  upper  two  diagrams,  this  condition  is  attained, 


s^±: 


3i2'i'T"|'r  Tsn  ny'i'i'i" 


f 


132  MODERN  DRILLING   PRACTICE 

while  in  the  lower  two  there  is  failure  to  secure  the  required 
condition. 

Measuring  or  Gaging  Drills  after  Grinding.  —  In  Fig.  5  are 
shown  various  methods  of  gaging  twist  drills  after  grinding  in 
order  to  determine  the  accuracy  of  the  point  angle,  the  clearance, 
etc.  At  A  is  shown  a  simple  gage  made  by  the  Standard  Tool 
Co.  for  measuring  the  accuracy  of  the  5g-degree  point  angle;  this 
gage  is  also  graduated  in  such  a  way  that  it  may  be  used  to 
measure  the  length  of  the  two  cutting  edges  to  see  that  these  are 
equal.  Used  in  the  manner  shown  at  B,  this  gage  can  also  be 
employed  to  measure  the  center  angle,  i.e.,  the  angle  made  by 
the  chisel  point  with  the  cutting  edges  of  the  drill.  Although 
the  included  angle  of  this  gage  is  only  118  degrees  and  an  angle 
of  130  degrees  is  required  between  the  chisel  point  and  the 
cutting  edges  of  the  drill,  the  use  of  the  gage  in  this  way  enables 
a  very  close  estimate  to  be  made  of  the  accuracy  of  the  angle 
of  the  chisel  point,  and  it  will  be  recalled  that  this  angle  de- 
termines the  clearance  provided  for  the  cutting  edges. 

At  C  is  shown  how  a  protractor  may  be  used  to  measure  the 
point  angle,  and  this  illustration  is  self-explanatory.  Another 
method  of  measuring  the  angle  of  the  drill  point  is  shown  at  D, 
and  this  method  also  affords  a  means  of  obtaining  an  idea  of  the 
accuracy  of  the  clearance  provided  behind  the  cutting  edges. 
The  length  of  each  cutting  edge  is  first  measured  with  the  scale 
to  see  that  they  are  equal;  and,  if  so,  the  drill  is  supported  as 
shown  and  measurements  are  made  at  each  side,  as  indicated  in 
the  illustration.  If  these  measurements  are  equal,  it  shows  that 
the  point  angle  is  the  same  at  both  sides  of  the  drill.  This 
method  may  also  be  used  to  measure  the  clearance  provided 
for  each  cutting  edge  by  placing  the  drill  point  beside  the  scale 
as  shown,  and  then  slowly  revolving  the  drill.  If  the  clearance 
at  each  side  is  not  the  same,  it  will  be  indicated  by  a  difference 
in  the  relative  positions  of  the  drill  and  scale  for  corresponding 
positions  of  the  drill.  It  must  be  borne  in  mind  that  this  method 
indicates  the  clearance  provided  at  the  heel  of  the  drill  only, 
and  while  this  clearance  may  be  correct,  there  may  still  be 
a  serious  error  in  clearance  near  the  drill  point.  At  E  and  F 


DRILL  GRINDING  133 

are  shown  two  types  of  gages  made  by  the  Morse  Twist  Drill  & 
Machine  Co.  for  testing  the  angle  of  drill  point;  these  illustra- 
tions show  clearly  the  method  of  using  the  gages  without  re- 
quiring a  description. 

Use  of  Drill  Grinding  Machines.  —  There  are  a  number  of 
drill  grinding  machines  on  the  market  which  are  properly  de- 
signed to  provide  for  accurately  securing  the  required  contour 
for  the  drill  point.  Drills  ground  on  such  machines  ought  to 
meet  all  of  the  requirements  to  which  attention  has  been  called. 
It  should  scarcely  be  necessary  to  call  attention  to  the  fact  that 
it  is  very  important  for  the  drill  grinding  machine  to  be  kept  in 
proper  adjustment  in  order  to  produce  the  expected  results; 
but  it  was  recently  stated  that  a  certain  shop  purchased  its 
twist  drills  from  a  well-known  manufacturing  firm,  and  an  in- 
vestigation made  to  determine  the  cause  of  breakage  of  drills 
for  which  a  replacement  claim  had  been  made  revealed  the  fact 
that  the  drill  grinding  machine  used  in  this  shop  was  so  badly 
out  of  adjustment  that  it  failed  to  produce  drill  points  of  the 
required  form.  When  attention  was  called  to  the  fact  that  the 
broken  drills  had  been  improperly  ground,  the  possibility  of 
such  a  condition  was  promptly  denied,  as  it  was  asserted  that 
"  they  had  been  sharpened  on  a  drill  grinder."  Subsequently 
this  machine  was  properly  adjusted  and  a  responsible  mechanic 
was  employed  to  do  all  of  the  drill  grinding,  and  since  that 
time  there  has  been  a  marked  falling  off  in  the  number  of  drills 
broken  in  the  shop.  Several  manufacturers  of  twist  drills  who 
have  had  a  great  deal  of  experience  with  troubles  which  may 
result  through  improper  grinding  state  that,  in  shops  using  any 
considerable  number  of  drills,  the  wages  of  an  experienced 
mechanic,  placed  in  charge  of  all  drill  grinding  and  held  respon- 
sible for  the  results  obtained,  would  be  more  than  paid  by  the 
saving  in  broken  drills. 

How  to  Grind  a  Drill  by  Hand.  —  It  is  a  difficult  matter  to 
grind  a  drill  by  hand  and  secure  the  desired  results  without 
taking  altogether  too  much  time  in  performing  the  grinding 
operation,  as  previously  mentioned.  Nevertheless,  the  mechanic 
who  makes  an  intelligent  study  of  the  requirements  of  drill 


134  MODERN  DRILLING  PRACTICE 

grinding  can  learn  to  grind  a  drill  by  hand  after  he  has  had 
enough  experience  to  enable  him  to  acquire  the  necessary  de- 
gree of  dexterity.  One  method  of  grinding  drills  by  hand, 
which  is  capable  of  giving  satisfactory  results,  is  to  hold  first 
one  lip  of  the  drill  and  then  the  other  against  the  grinding  wheel 
so  that  a  flat  clearance  surface  is  ground  at  the  back  of  each 
cutting  edge.  In  doing  this  work  great  care  should  be  taken 
not  to  change  the  angle  which  the  chisel  point  of  the  drill  makes 
with  the  cutting  edges,  as  it  is  the  angle  of  the  chisel  point  which 
determines  the  amount  of  clearance  provided  for  the  cutting 
edges.  After  these  flat  clearance  surfaces  have  been  ground, 
the  mechanic  very  carefully  swings  the  drill  back  and  forth  so 
that  the  flat  ground  surfaces  are  blended  into  the  remainder  of 
the  surface  back  of  each  cutting  edge.  This  method  of  grinding 
will  not  produce  a  drill  point  which  appears  to  approximate 
closely  the  form  produced  on  a  drill  grinding  machine,  but  the 
results  obtained  with  a  drill  ground  in  this  way  will  often  be 
far  more  satisfactory  than  those  resulting  from  the  use  of  a 
drill  ground  by  hand,  where  the  mechanic  has  attempted  to 
secure  a  closer  approximation  of  the  original  form  of  the  drill 
point  through  swinging  the  drill  back  and  forth  on  the  surface 
of  the  grinding  wheel. 

If  the  mechanic  attempts  to  grind  a  drill  by  hand  and  dupli- 
cate the  movement  secured  through  the  use  of  a  drill  grinding 
machine,  the  proper  method  of  procedure  is  as  follows:  The 
drill  is  held  between  the  thumb  and  index  finger  of  the  left  hand 
at  a  short  distance  back  of  the  point,  and  the  hand  is  steadied 
by  the  tool-rest  of  the  tool  grinder.  The  drill  is  held  at  such 
an  angle  to  the  grinding  wheel  that  the  surface  of  the  drill  point 
rests  flat  against  the  wheel,  and  great  care  must  be  taken  to 
have  the  chisel  point  of  the  drill  in  a  vertical  position;  in  other 
words,  the  cutting  edge  of  the  drill  is  inclined  upward.  With 
the  drill  held  in  this  position,  the  mechanic  grips  the  shank  be- 
tween the  thumb  and  index  finger  of  his  right  hand  and  slowly  os- 
cillates the  drill  about  an  imaginary  axis,  between  the  thumb  and 
index  finger  of  his  left  hand,  taking  care  to  keep  the  chisel  point 
vertical  at  all  times.  After  grinding  one  side  of  the  drill  in  this 


Jljg 

law  , 


«  0° 


fill  I 

Iis2§ 

sin? 

531SJ 

.  3*0  -d  a 


* 

O,^     0)     »HH 

O  O  W)  ft  _. 


Q<  ^p< 


I3S 


136  MODERN  DRILLING  PRACTICE 

way,  the  drill  is  turned  over  so  that  the  other  side  may  be  ground. 
This  method  can  be  used  with  extremely  satisfactory  results 
by  men  who  have  had  a  great  deal  of  experience  in  drill  grind- 
ing, but  it  is  probable  that  the  average  mechanic  will  secure 
better  results  through  the  method  of  hand  grinding  referred 
to  in  the  preceding  paragraph.  In  any  case,  hand  grinding  is 
not  recommended  for  the  average  shop,  as  the  superior  speed 
and  quality  of  workmanship  obtained  through  the  use  of  drills 
ground  on  a  drill  grinding  machine  are  quite  sufficient  to  war- 
rant the  investment  in  an  equipment  of  this  kind. 

Effect  of  Improper  Drill  Grinding.  —  A  better  idea  of  the 
actual  effect  of  improper  drill  grinding  will  be  gathered  by 
reference  to  Fig.  6,  which  shows  various  conditions  of  the  drill 
point  which  are  made  possible  through  correct  or  incorrect 
grinding.  At  A  is  shown  a  drill  ground  with  the  proper  clearance 
for  the  cutting  edges,  and  at  B  is  shown  a  drill  on  which  an 
insufficient  amount  of  clearance  has  been  furnished  at  the 
center,  although  there  is  plenty  of  clearance  at  the  heel  of  each 
cutting  edge.  It  will  be  recalled  that  the  angle  of  the  chisel 
point,  i.e.,  the  line  separating  the  two  faces  of  the  drill  point, 
indicates  the  amount  of  clearance  provided  for  the  cutting  edges, 
and  at  C  is  shown  what  is  likely  to  happen  to  a  drill  where  the 
angle  of  the  chisel  point  and  clearance  of  the  cutting  edges  are 
insufficient.  This  drill  had  plenty  of  clearance  at  the  heel,  but 
very  little  clearance  at  the  center,  with  the  result  that  it  was 
split  up  the  center.  A  better  idea  of  the  way  in  which  the 
angle  of  the  chisel  point  indicates  the  amount  of  clearance  will 
be  gathered  by  referring  to  the  two  end  views  of  the  drill  shown 
at  D  and  E.  At  D  is  shown  a  drill  in  which  the  chisel  point 
has  been  ground  to  make  an  angle  of  130  degrees  to  the  cutting 
edges,  which  gives  a  sufficient  amount  of  clearance,  while  at  E 
the  angle  formed  is  only  100  degrees,  and  this  drill  has  insuffi- 
cient clearance. 

Most  twist  drills  are  made  in  such  a  way  that  the  web  at 
the  center  increases  in  thickness  as  the  length  of  the  drill  is 
gradually  decreased  in  sharpening.  On  account  of  this  in- 
crease in  web  thickness,  mechanics  have  acquired  the  practice 


DRILL   GRINDING  137 

of  grinding  away  the  web  at  the  drill  point  or  "  thinning  "  the 
web,  as  the  process  is  commonly  called.  A  great  deal  of  trouble 
is  likely  to  result  from  this  practice  of  thinning  the  drill  point, 
due  to  the  excessive  amount  of  metal  which  is  often  ground 
away.  Where  skilled  mechanics  do  the  work  and  are  careful 
to  grind  away  only  a  sufficient  amount  of  metal  to  maintain 
the  web  thickness  equal  to  the  original  thickness  of  the  web  at 
the  point  of  the  drill  when  it  was  new,  this  practice  is  not  detri- 
mental; but  if  an  excessive  amount  of  grinding  is  done,  it  is 
almost  sure  to  produce  undesirable  results.  At  F  is  shown  a 
drill  point  in  which  the  web  has  been  properly  thinned  to  reduce 
it  to  the  original  dimension,  while  at  G  is  shown  a  drill  point  on 
which  thinning  has  been  carried  to  excess.  A  drill  ground  in 
this  way  is  extremely  liable  to  break  through  splitting  up  the 
center,  and  such  a  drill  will  also  require  more  power  to  drive  it, 
due  to  trouble  experienced  in  clearing  the  chips.  While  pro- 
vision of  the  necessary  amount  of  clearance  for  the  cutting 
edges  of  a  drill  is  highly  important,  it  is  equally  important  not 
to  provide  too  much  clearance,  because  in  such  cases  an  in- 
sufficient amount  of  metal  is  left  behind  the  cutting  edges  and 
trouble  is  likely  to  be  experienced  through  chipping  the  drill. 
At  //  is  shown  another  drill  which  has  the  proper  amount  of 
clearance.  Comparison  with  drill  I  shows  that  the  latter  has 
insufficient  clearance,  thus  causing  the  heel  to  drag;  conse- 
quently, the  drill  will  give  very  unsatisfactory  results  in  opera- 
tion and  may  not  cut  at  all. 

Causes  of  Broken  Drills.  —  The  conditions  of  service  under 
which  a  twist  drill  operates  are  more  severe  than  those  imposed 
upon  almost  any  other  type  of  cutting  tool,  because  the  drill  must 
of  necessity  be  of  such  size  that  it  can  enter  the  hole  in  which  it 
works,  while  its  cross-section  has  to  be  greatly  reduced  in  order 
to  provide  the  required  clearance  for  the  escape  of  chips.  De- 
spite this  fact,  it  is  quite  probable  that  the  average  twist  drill 
receives  as  little  consideration  as  any  tool  used  in  the  machine 
shop,  there  being  a  somewhat  general  impression  among  me- 
chanics that  a  twist  drill  is  sold  ready  for  use  and  can  properly 
be  expected  to  continue  to  give  satisfactory  service  regardless 


138 


MODERN  DRILLING  PRACTICE 


of  the  way  in  which  it  is  handled.  The  fallacy  of  this  idea  is 
clearly  shown  by  the  tremendous  wastage  which  occurs  every 
year  through  breaking  drills  as  a  result  of  improper  use.  Refer- 
ence has  already  been  made  to  the  conditions  that  must  be  ful- 
filled in  order  for  a  drill  to  give  efficient  service,  and  if  the  grind- 
ing operation  is  not  conducted  so  that  these  conditions  are  ful- 
filled, an  abnormal  strain 
is  likely  to  be  placed  upon 
the  drill  which  may  rap- 
idly assume  sufficient  pro- 
portions to  cause  it  to  be 
broken. 

There  is  another  point 
which  is  likely  to  be  re- 
sponsible for  breaking  of 
drills;  namely,  the  spring 
and  lost  motion  in  drill- 
ing machines  due  to  im- 
proper design.  The  way 
in  which  this  condition  is 
likely  to  cause  breakage 
of  drills  will  be  under- 
stood by  reference  to 
Fig.  7.  Assuming  that 
the  members  of  a  drilling 
machine  can  be  sprung  o.oio  inch  as  a  result  of  back-pressure 
exerted  by  the  drill  while  in  operation,  then,  during  the  time 
that  this  spring  is  being  imposed  upon  the  machine  mem- 
bers, the  rate  at  which  the  drill  point  is  fed  into  the  work  is 
represented  by  the  normal  feed  per  revolution  minus  the  amount 
of  spring  imposed  upon  the  members  of  the  drilling  machine 
per  revolution. 

When  this  lost  motion  has  been  taken  up,  the  drill  will  con- 
tinue to  operate  at  the  normal  rate  of  feed  until  such  a  time 
as  the  drill  point  breaks  through  the  work  at  the  bottom  of 
the  hole.  When  this  result  takes  place  there  will  be  a  sudden 
reduction  of  back-pressure  exerted  by  the  drill,  with  the  result 


—  0  001 

JKU  ULVOLUTION 

—0.001 

>j 

),  WHEN  FEED 
f     IS  NORMAL 

) 

+0.  001  

4-0.  002  

2ND  REVOLUTION 

+0  003 

- 

+0  001 

Machinery 

Fig.  7.  Diagram  showing  how  Spring  in 
Drilling  Machine  causes  Excessive  Rate 
of  Feed,  which  may  break  the  Drill 


DRILL  GRINDING  139 

that  the  strained  members  of  the  drilling  machine  will  suddenly 
react;  now,  under  these  conditions,  the  rate  of  feed  will  be  the 
normal  rate  provided  by  the  gearing  in  the  feed-box  plus  the 
increase  due  to  a  sudden  release  of  the  strain  on  members  of 
the  drilling  machine.  This  sudden  increase  in  the  rate  of  feed 
as  the  drill  breaks  through  is  the  reason  why  so  many  drills  are 
broken  at  just  this  point,  and  not  because  there  is  any  tendency 
for  the  bottom  surface  of  the  work  to  catch  the  cutting  lips  of 
the  drill  according  to  a  somewhat  general  impression  which 
exists  among  mechanics  who  have  given  very  little  thought  to 
the  situation. 

Now,  in  the  case  of  a  drilling  machine  where  the  parts  have 
not  been  designed  in  a  way  which  assures  the  required  degree 
of  rigidity,  it  is  obvious  that  one  of  two  conditions  must  exist: 
either  the  rate  of  feed  must  be  made  the  maximum  safe  rate 
for  the  drill  minus  the  amount  of  additional  feed  imposed  upon 
the  drill  during  the  time  that  it  is  breaking  through  the  hole 
at  the  bottom  of  the  work,  or  else  the  risk  must  be  run  of  break- 
ing a  number  of  drills  through  this  sudden  increase  in  the  rate 
of  feed  while  the  operation  is  being  finished.  Obviously,  the 
decision  of  any  experienced  production  manager  will  be  that 
neither  condition  will  meet  his  requirements.  He  will  insist 
upon  the  purchase  of  drilling  machines  of  sufficiently  rigid 
construction  so  that  the  amount  of  back-pressure  exerted  by 
the  drill  point  while  penetrating  the  work  will  not  be  sufficient 
to  cause  an  appreciable  amount  of  spring. 

Determination  of  Magnitude  of  Feed  Pressure  and  Torsion. 
-In  connection  with  research  work  conducted  by  engineers 
of  the  Cleveland  Twist  Drill  Co.  to  determine  the  magnitude 
of  strains  imposed  upon  a  twist  drill  due  to  feed  pressure  and 
torsional  resistance,  a  special  drilling  machine  was  constructed 
in  such  a  way  that  the  table  of  the  machine  rests  upon  a  piston- 
rod  connected  to  a  piston  entering  a  cylinder  filled  with  oil. 
When  a  drill  mounted  in  the  spindle  of  this  machine  is  driven 
into  a  piece  of  work  supported  on  the  table,  it  will  be  obvious 
that  pressure  exerted  by  the  drill  results  in  introducing  a  corre- 
sponding amount  of  pressure  on,  the  piston,  and  hence  on  the 


140  MODERN  DRILLING  PRACTICE 

oil  contained  in  the  cylinder.  A  recording  pressure  gage  con- 
nected to  this  cylinder  makes  it  possible  to  calculate  the  amount 
of  pressure  exerted  by  the  drill  while  penetrating  the  work. 
To  prevent  rotation  of  the  table  of  this  special  drilling  machine, 
a  radial  arm  is  carried  out  from  the  table  and  provided  with  a 
piston-rod  connecting  with  a  piston  in  a  second  oil  cylinder. 
A  recording  pressure  gage  is  also  connected  to  this  cylinder, 


Machinery 


Fig.  8.  Combined  Torsion  and  Feed-pressure  Chart  for  ij-inch  Drill 
operated  in  Special  Testing  Machine  which  Registers  Torsion 
and  Feed  Pressure  on  Recording  Hydraulic  Pressure  Gages 

by  means  of  which  it  is  possible  to  measure  the  torsional  stress 
upon  the  drill. 

Fig.  8  shows  a  combined  feed-pressure  and  torsion  chart 
for  a  ij-inch  drill  operated  in  this  machine,  and  this  chart 
illustrates  very  clearly  another  important  consideration  in  pre- 
venting broken  drills  as  a  result  of  spring  in  the  drilling  ma- 
chine members  to  which  reference  was  made  in  a  preceding 
paragraph.  This  is  the  provision  of  a  proper  amount  of  clear- 


DRILL   GRINDING  141 

ahce  on  the  drill  surfaces  behind  the  cutting  edges.  Reference 
to  this  pressure-torque  chart  will  make  it  apparent  that  there 
is  a  pronounced  difference  in  feed  pressure  and  torsion  for 
each  of  the  pairs  of  curves  recorded  on  this  chart.  These 
differences  in  feed  pressure  and  torsion  are  due  to  the  fact 
that  the  drill  used  in  making  one  pair  of  curves,  where  the 
feed  pressure  and  torsion  are  greater,  was  ground  on  a  ma- 
chine which  provides  less  clearance  for  the  drill  point  than  is 
the  case  on  the  drill  grinding  machine  which  ground  the  drill 
used  in  drawing  the  pair  of  curves  where  feed  pressure  and 
torsion  are  less.  Obviously,  this  lays  emphasis  upon  the  im- 
portance of  grinding  drills  on  a  machine  which  will  provide 
the  required  amount  of  clearance  to  enable  satisfactory  opera- 
tion to  be  secured  under  the  maximum  amount  of  feed  that 
will  be  used  under  the  most  severe  conditions  of  operation, 
without  unduly  increasing  the  pressure  and  consequent  spring 
in  the  drilling  machine.  In  this  connection,  the  reader's  atten- 
tion is  directed  to  the  paragraph  on  drill  grinding  which  ex- 
plains methods  of  measuring  the  amount  of  clearance  provided 
on  the  drill  point  to  make  sure  that  this  conforms  with  the 
recommendations  of  firms  specializing  in  the  manufacture  of 
drills.  In  the  case  of  the  feed-pressure  curves  in  the  chart, 
it  will  be  seen  that  the  pressure  first  runs  up  rapidly  and  then 
takes  a  peculiar  drop  before  assuming  the  normal  condition. 
This  drop  is  due  to  the  fact  that,  near  the  center  of  the  drill, 
the  cutting  edges  have  practically  no  rake;  the  pressure  runs 
up  while  the  point  of  the  drill  is  entering  the  work,  and  when 
approaching  the  periphery,  where  there  is  a  considerable  amount 
of  rake,  this  rake  helps  to  pull  the  drill  into  the  work,  thus 
reducing  the  feed  pressure  and  producing  the  peculiar  dip  seen 
in  the  feed-pressure  curves. 


CHAPTER  VIII 

DRILLING   MACHINES   APPLIED   TO    GENERAL 
MANUFACTURING   OPERATIONS 

THERE  are  many  shop  superintendents  and  men  in  charge 
of  the  planning  of  machining  operations  who  do  not  realize  the 
full  scope  of  work  which  may  be  efficiently  handled  on  drilling 
machines.  In  many  shops  gratifying  results  are  obtained  in 
the  performance  of  such  operations  as  drilling,  counterboring, 
reaming,  and  tapping;  but  most  factory  executives  have  a  well 
defined  idea  of  what  constitutes  "  drill  press  work,"  and  the  use 
which  they  make  of  their  drilling  machines  is  confined  to  those 
pieces  which  come  under  this  arbitrary  classification.  Those  in 
charge  of  the  machine  shops  in  some  progressive  manufacturing 
plants  have  recently  broken  away  from  this  idea  and  have 
extended  the  use  of  drilling  machines  to  provide  for  handling 
many  operations  for  which  turret  lathes,  engine  lathes,  and  other 
types  of  machine  tools  were  formerly  employed.  In  so  doing, 
the  quality  of  workmanship  has  been  kept  up  to  the  previous 
standards  and  in  practically  every  case  rates  of  production 
have  been  materially  increased.  There  are  few  shops  where 
a  wider  range  of  manufacturing  operations  are  handled  on 
heavy-duty  drilling  machines  or  where  higher  rates  of  produc- 
tion are  obtained  on  this  type  of  machine  than  at  the  plant 
of  S.  F.  Bowser  &  Co.,  Inc.,  Fort  Wayne,  Ind.  This  concern 
operates  a  battery  of  twenty-eight  of  the  No.  310  high-duty 
drilling  machines  built  by  Baker  Bros.,  Toledo,  Ohio,  and  the 
organization  of  systems  for  the  expeditious  handling  of  work 
and  the  development  of  jigs,  fixtures,  and  special  cutting  tools 
for  use  on  these  machines  has  been  carried  to  a  high  degree 
of  perfection. 

Range  of  Work  done  on  Drilling  Machine.  —  Many  shop 
men  who  have  formed  their  own  opinions  as  to  what  constitutes 
the  range  of  work  that  can  be  efficiently  handled  on  drilling 

142 


GENERAL  MANUFACTURING  OPERATIONS  143 

machines  would  be  greatly  surprised  at  the  results  obtained  in 
the  Bowser  shops.  Two  points  would  doubtless  be  the  first 
to  attract  attention;  namely,  the  great  variety  of  machining 
operations  that  are  performed,  and  the  extremely  high  rates  of 
production  which  are  secured  with  a  relatively  small  labor  cost 
for  the  operation  of  machines.  In  addition  to  the  familiar 
operations  of  drilling,  counterboring,  reaming,  tapping,  etc.,  a 
variety  of  other  operations,  including  turning,  threading,  facing, 
and  boring  are  performed  under  conditions  that  give  very  satis- 
factory results  from  the  standpoints  of  finish,  accuracy,  and 
rates  of  production. 

Arrangement  of  Machines.  —  There  are  necessarily  a  number 
of  details  concerning  the  operation  of  this  department  which 
vary  according  to  the  character  of  the  work,  but  the  basic 
principles  governing  the  handling  of  all  classes  of  work  are  as 
follows:  The  machines  are  set  up  in  one  row  and  placed  close 
enough  together  so  that  sheet-metal  troughs  extend  from  table 
to  table  of  adjacent  machines.  As  a  result,  when  the  operation 
on  one  machine  has  been  completed,  the  work  may  be  pushed 
across  to  the  next  machine  with  a  minimum  expenditure  of  time 
and  exertion  on  the  part  of  the  operator.  The  parallel  between 
this  plan  and  the  operation  of  turret  lathes  for  handling  the 
same  work  will  be  obvious.  Instead  of  indexing  a  turret  to 
bring  successive  tools  into  operation,  the  work  is  moved  along 
under  the  spindles  of  machines  carrying  the  required  tools. 
Operations  are  conducted  on  the  progressive  system,  but  al- 
though many  parts  are  handled  which  require  a  considerable 
number  of  operations  to  complete  them  ready  for  the  assembling 
department  —  running  as  high  as  twelve  operations  in  some 
cases  —  it  is  never  found  advisable  to  have  so  many  machines 
working  on  the  same  piece  at  one  time. 

Number  of  Machines  used  Progressively.  —  Before  giving 
the  subject  serious  consideration,  it  would  doubtless  appear 
that  the  most  efficient  results  would  be  obtained  by  setting  up  a 
sufficient  number  of  machines  to  enable  the  work  to  be  com- 
pleted without  the  necessity  of  intermediate  handling  between 
the  performance  of  different  series  of  operations.  Experience 


144  MODERN  DRILLING  PRACTICE 

has  shown,  however,  that  on  the  average  classes  of  work  handled 
on  these  machines,  one  operator  is  able  to  take  care  of  four 
machines.  Accepting  this  as  a  basis  of  operation,  and  consider- 
ing the  case  of  a  piece  in  which  twelve  operations  are  required 
to  finish  the  machining,  it  at  once  becomes  apparent  that  three 
operators  and  three  groups  of  four  machines  would  be  necessary. 
So  long  as  there  is  no  interruption  in  the  process  of  manufacture, 
the  greatest  efficiency  would  result  through  setting  up  twelve 
machines  so  that  the  work  could  be  handed  along  progressively 
until  the  last  operation  was  completed,  after  which  the  pieces 
would  be  transferred  to  the  painting  department  preparatory 
to  being  assembled.  As  a  matter  of  fact,  the  method  of  proce- 
dure would  probably  be  to  handle  the  first  four  operations  as 
if  their  completion  resulted  in  finishing  the  work.  This  set  of 
four  machines  would  then  be  dismantled  and  set  up  for  the 
second  set  of  four  operations,  and  after  these  operations  had 
been  completed,  the  machines  would  again  be  dismantled  and 
set  up  for  the  final  operations.  The  reason  for  adopting  this 
method  is  that  experience  has  shown  that,  where  more  than 
four  machines  are  operated  at  a  time,  delays  resulting  from 
the  breakage  of  tools  on  any  one  machine  or  the  temporary 
absence  of  one  operator  from  his  group  of  machines  would 
result  in  a  congestion  of  work  and  delay  of  one  or  more  of  the 
other  operators,  which  would  far  more  than  offset  the  time 
saved  by  the  avoidance  of  what  might  appear  to  be  two  un- 
necessary transfers  of  the  work  from  machines  to  trucks,  and 
vice  Versa.  Another  advantage  of  subdividing  the  total  series 
of  machining  operations  in  this  way  is  that  the  percentage  of 
the  total  machine  equipment  used  on  a  single  piece  at  any  one 
time  is  greatly  reduced.  As  there  are  a  large  number  of  differ- 
ent parts  constantly  going  through  the  shop,  it  would  be  poor 
practice  to  tie  up  as  many  as  twelve  machines  out  of  twenty- 
eight  on  a  single  job. 

No  difficulty  has  been  experienced  in  using  four  machines 
for  a  piece,  regardless  of  the  number  of  operations.  Pieces 
with  one  operation  would  have  four  sets  of  tools  and  fixtures; 
pieces  with  two  operations  would  have  two  sets  of  tools ;  and 


GENERAL  MANUFACTURING  OPERATIONS  145 

pieces  with  six  or  ten  operations  would  have  the  tools  doubled 
for  the  last  two  operations,  which  would  enable  the  operator 
to  do  the  last  two  operations  on  four  machines,  finishing  two 
pieces  at  a  time.  With  pieces  requiring  three,  five,  seven,  or 
nine  operations,  etc.,  it  is  usually  possible  to  combine  two  of 
the  operations  so  as  to  fit  an  even  number  of  machines,  or 
else,  in  cases  where  there  is  one  long  operation,  to  set  up  two 
machines  for  this,  the  operator  having  time  to  perform  the 
other  two  operations  of  this  group  on  two  pieces  while  either 
of  the  first  two  machines  is  performing  One  operation.  An  ex- 
ample of  nine  operations  being  performed  on  eight  machines 
is  shown  on  piece  No.  15  of  the  accompanying  lists  of  parts 
representing  various  examples  of  work  done  on  drilling  ma- 
chines, an  example  of  a  piece  with  three  operations  being  per- 
formed to  advantage  on  four  machines  is  shown  on  part  No.  2 ; 
and  an  example  of  a  piece  with  five  operations  being  performed 
on  four  machines  is  shown  on  part  No.  4.  The  detailed  method 
of  operations  on  this  piece  is  as  follows : 

Order  of  Operations.  —  Referring  to  Fig.  i ,  it  will  be  seen 
that  four  machines  are  used,  the  boring  operation  being  per- 
formed on  the  first,  turning  on  the  second,  tapping  on  the  third, 
and  threading  on  the  fourth.  The  third  operation  is  really  a 
double  one,  because  the  piece  is  tapped  with  a  taper  pipe  tap 
from  each  side.  The  machine  for  this  operation  has  a  sliding 
fixture  with  provisions  for  holding  two  pieces,  one  of  these  being 
inverted.  The  order  followed  by  the  operator  of  this  group  of 
machines  in  going  about  his  work  is  as  follows:  (i)  Remove 
bored  piece  from  machine  No.  i  and  set  up  fresh  blank.  (2) 
Remove  turned  piece  from  machine  No.  2  and  set  up  bored 
piece  from  machine  No.  i.  (3)  Remove  piece  from  3-6  and 
place  in  position  marked  by  a  cross  between  3-6  and  4  in  Fig.  i ; 
remove  piece  from  3-A  and  place  in  position  3-6;  take  bored 
and  turned  piece  from  machine  No.  2  and  place  in  position  3 -A; 
slide  fixture  until  spindle  is  over  3-A  and  start  machine  No.  3. 
(4)  Remove  finished  piece  from  machine  No.  4  and  set  up  piece 
which  was  set  in  position  marked  by  cross  between  machines 
Nos.  3  and  4.  (5)  Go  back  to  machine  No.  3,  hole  at  3-A 


146 


MODERN  DRILLING  PRACTICE 


being  tapped  by  this  time,  push  fixture  over  and  start  spindle  in 
piece  in  position  3-6.  (6)  Return  to  machine  No.  i. 

Another  point  which  helps  out  the  machining  of  pieces  where 
it  is  necessary  to  perform  a  number  of  operations  is  the  pos- 
sibility of  using  portable  machines,  such  as  tappers,  etc.,  to 
take  a  fifth  and  seventh  operation.  Piece  No.  n  in  the 
"  List  of  Parts,  Order  of  Machining  Operations,  and  Rates  of 
Production  "  is  an  example  of  this.  With  such  highly  system- 
atized methods  for  the  performance  of  a  sequence  of  opera- 
tions, it  is  believed  by  the  management  of  the  Bowser  factory 
that  the  highest  rate  of  production  that  is  possible  is  obtained 
from  each  machine. 

Organization  of  Department  Management.  —  Reference  has 
already  been  made  to  the  fact  that,  in  operating  these  machines, 
it  is  the  practice  never  to  have  more  than  four  machines  work- 


SPINDLE 

I 

X 

1 

2 

3-A        3-B 

4 
Machinery 

Fig.  i.  Diagram  illustrating  Procedure  in  moving  Work  from 
Machine  to  Machine  to  keep  all  Machines  in  Group  con- 
stantly in  Operation 

ing  on  the  same  piece;  however,  it  occasionally  happens  that 
the  length  of  operations  on  a  group  of  machines  is  such  that  the 
operator  can  perform  the  first  operation  on  the  group  of  four 
machines  next  to  his  own  in  less  time  than  the  other  operator 
can  perform  the  remaining  three,  in  which  case  the  machines 
are  divided  up  -five  and  three  between  the  two  operators,  al- 
though the  parts  being  machined  each  require  four  machines. 
There  is  a  set-up  man  in  charge  of  the  department  who  is  under 
the  jurisdiction  of  the  general  foreman,  and  it  is  the  duty  of 
this  man  to  assist  the  operator  in  dismantling  his  machine  at 
the  completion  of  each  job  and  in  setting  up  the  new  jobs.  He 
also  sees  that  sharp  tools  are  furnished  to  the  operators  at  such 
times  as  they  need  them  and  can  also  substitute  for  any  of  the 
regular  machine  operators  at  such  times  as  the  latter  are  away, 


GENERAL  MANUFACTURING  OPERATIONS 


147 


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154 


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Fig.  2.     Tapping  Machine  mounted  on  Skid  to  t>e  handled  by  Elevat- 
Truck, 


mg 


and  equipped  with  Individual  Motor  Drive 


in  order  to  keep  all  the  machines  constantly  employed  during 
the  working  days.  Figs.  2  and  3  show  the  application  of  portable 
machines  for  performing  an  extra  operation  for  which  a  machine 
is  not  available. 


GENERAL  MANUFACTURING  OPERATIONS 


155 


Special  Equipment  for  Machines.  —  Mention  has  already  been 
made  of  the  fact  that  the  machines  used  in  the  plant  referred  to 
are  the  Baker  No.  310  high-duty  drilling  machines.  Standard 
machines  were  purchased,  but  in  order  to  adapt  them  for  the 
special  requirements  of  this  work  it  was  found  necessary  to 
apply  some  additional  equipment.  Actual  changes  made  in 


Fig.  3.  Arbor  Press  mounted  on  Skid  so  that  it  can  be  set  in 
Place  to  press  in  Bushings  during  Performance  of  a  Se- 
quence of  Machining  Operations 

the  machine  details  include  the  following:  Provision  of  special 
gears  in  the  feed  train  to  allow  for  cutting  threads  of  the  desired 
pitches,  including  the  nj  pipe  threads;  provision  of  an  auto- 
matically-operated air  cylinder  on  each  machine  for  shifting 
the  double  belt  drive,  to  provide  for  reversing  the  direction  of 
rotation  for  backing  out  taps  and  backing  off  threading  dies; 
and  the  provision  of  a  special  feed-release  mechanism  which 
disengages  the  feed-clutch  but  allows  the  spindle  to  continue 


156  MODERN  DRILLING  PRACTICE 

rotating  for  the  necessary  length  of  time  to  insure  the  removal 
of  tool-marks  when  performing  facing,  chamfering,  and  counter- 
boring  operations. 

In  this  connection,  it  might  be  mentioned  that  a  special  ar- 
rangement of  counterweights  is  provided  which  are  much  lighter 
than  the  standard  counterweights  furnished  on  the  machine. 
These  weights  are  of  the  slotted  disk  type  and  the  number  of 
weights  used  can  be  such  that  the  boring  tool,  tap,  or  die  can 
either  be  just  floated  off  the  work  or  actually  returned  to  the 
starting  position  automatically,  so  that  all  the  operator  has  to 
do  is  to  pull  the  spindle  down  and  throw  in  his  feed-lever.  The 
capstan  placed  in  the  base  of  each  machine  under  the  counter- 
weight provides  for  regulating  the  height  to  which  the  spindle  is 
raised,  so  that  the  height  of  the  spindle  in  its  "  up  "  position 
can  be  made  to  suit  each  job.  It  also  prevents  the  spindle 
quill  from  striking  the  top  of  the  machine  in  cases  where  heavy 
counterweights  are  used.  This  is  accomplished  by  raising  or 
lowering  the  capstan  so  that  it  stops  the  fall  of  the  counter- 
weight at  just  the  required  point. 

Special  Provision  for  Threading  and  Tapping.  —  On  these 
machines,  threading  and  tapping  operations  are  performed  on 
work  where  it  is  required  to  cut  from  eight  to  twenty  threads 
per  inch.  On  the  Baker  high-duty  drilling  machines,  changes 
in  feed  are  obtained  by  first  placing  lever  A,  Fig.  4,  in  one  of  the 
three  positions  controlled  by  inserting  a  pin  into  holes  in  the  dial 
over  which  this  lever  rotates.  Any  of  the  rates  of  feed  obtained 
in  this  way  may  be  compounded  through  slip  gears  B,  C,  D, 
and  £,  which  have  27,  33,  20,  and  40  teeth,  respectively.  It 
will  be  apparent  that  both  pairs  of  gears  BC  and  DE  have  a 
total  .of  60  teeth,  so  that  they  may  be  placed  on  fixed  centers, 
and  by  transposing  gears  B  and  C  or  transposing  gears  D  and 
E,  the  three  available  rates  of  feed  obtained  for  different  set- 
tings of  lever  A  are  combined  to  give  a  total  of  1 2  feed  changes. 
The  total  range  of  feeds  runs  from  o.oio  to  0.050  inch  per  revolu- 
tion. This  mechanism  is  standard  for  the  Baker  drilling  ma- 
chines with  the  exception  of  the  fact  that  shafts  F  and  G  are 
made  5  inches  longer  than  the  standard  dimension  to  provide 


GENERAL  MANUFACTURING  OPERATIONS 


157 


for  introducing  special  gears  into  the  feed  train  in  order  to  secure 
the  desired  rate  of  advance  for  the  spindle  when  performing 
threading  and  tapping  operations,  which  are  the  only  operations 
for  which  these  special  gears  are  used. 


Fig.  4.     Arrangement  of  Special  Gears  introduced  into  Feed  Train 
to  Provide  for  Performing  Threading  and  Tapping  Operations 

When  the  machine  is  to  be  set  up  for  threading  or  tapping, 
the  first  step  is  to  remove  the  gears  from  shafts  F  and  G.  As 
a  substitute  for  these  two  gears,  one  of  the  special  change-gears 
H,  7,  or  /  is  introduced  into  the  feed  train;  this  special  gear 
has  twice  as  many  teeth  as  there  are  threads  per  inch  on  the 


158  MODERN  DRILLING  PRACTICE 

work  which  is  to  be  machined.  For  instance,  a  gear  with  23 
teeth  is  employed  for  threading  or  tapping  work  with  the  n| 
threads  per  inch  commonly  employed  on  pipe  fittings.  This 
gear  is  mounted  on  a  pull-pin  K,  after  which  quadrant  L  is 
pulled  up  to  readjust  the  position  of  the  gears  in  the  feed  train 
so  that  this  special  "  transposing  "  gear  for  threading  and  tap- 
ping operations  is  brought  into  mesh.  Before  starting  the 
threading  or  tapping  operation,  it  is  necessary  to  remove  the 
gears  from  shafts  F  and  G,  but,  if  so  desired,  the  transposing 
gear  may  be  left  in  place  on  the  pull-pin  K  when  the  machine 
is  used  on  other  classes  of  work*.  When  this  is  done,  the  gears 
are  simply  replaced  on  shafts  F  and  G  and  quadrant  L  is  dropped 
so  that  the  transposing  gear  is  no  longer  in  mesh.  Under  such 
conditions,  transmission  is  through  the  regular  feed-gears  on 
shafts  F  and  G.  Hooks  are  provided  for  the  feed  change-gears 
and  for  the  special  gears  for  threading  and  tapping,  so  that 
there  is  little  danger  of  their  being  misplaced  when  not  in  use. 

Automatic  Compressed-air  Reverse  for  Threading  and  Tap- 
ping. —  Reversal  of  the  direction  of  spindle  rotation  for  the  per- 
formance of  threading  and  tapping  operations  is  accomplished 
by  the  standard  arrangement  of  forward  and  reverse  belts 
furnished  on  the  Baker  high-duty  drilling  machines.  A  change 
in  the  method  of  operating  these  belts  has  been  provided,  how- 
ever; instead  of  using  a  hand-lever,  shifting  of  the  belts  is 
accomplished  automatically  by  compressed  air.  At  the  right- 
hand  side  of  two  machines  in  each  group  of  four,  there  will  be 
seen  a  small  air  cylinder  in  which  runs  a  piston  that  actuates 
the  belt  shifter. 

A  good  idea  of  the  way  this  mechanism  operates  will  be 
obtained-  from  Fig.  5  and  the  detail  views  of  the  control  mechan- 
ism, Fig.  6.  At  the  left-hand  side  of  the  machine,  within  con- 
venient reach  of  the  operator  there  will  be  seen  a  lever  A,  Fig.  5, 
which  actuates  the  air  valve.  When  this  lever  is  thrown  up 
it  opens  the  valve  to  admit  air  to  the  under  side  of  piston  J3, 
which  forces  this  piston  to  the  position  at  the  top  of  the  cylinder 
shown  in  Fig.  6.  Connected  to  the  piston-rod  there  is  a  rack  C 
which  meshes  with  a  pinion  on  shaft  D,  by  means  of  which  the 


GENERAL  MANUFACTURING  OPERATIONS 


159 


belt  shifter  is  actuated  to  throw  the  "  forward  "  driving  belt 
onto  its  tight  pulley,  while  the  "  reverse  "  driving  belt  is  shifted 
onto  its  loose  pulley.  When  it  is  desired  to  reverse  the  direc- 
tion of  rotation,  lever  A}  Fig.  5,  is  thrown  down  to  admit  air 
into  the  cylinder  above  the  piston,  with  the  result  that  this 
piston  is  forced  to  the  bottom  of  the  cylinder.  Through  rack 
C  and  the  meshing  pinion  carried  on  shaft  .D,  the  "  reverse  " 


Fig.  5.     Arrangement  of  Compressed-air  Control  for  Spindle  Reverse 
Mechanism  for  Threading  and  Tapping 

belt  is  thrown  onto  its  tight  pulley  and  the  "  forward  "  belt  is 
shifted  to  its  loose  pulley,  which  provides  for  backing  out  the 
tap  or  backing  off  the  threading  die. 

Automatic  Control  of  Mechanism.  —  So  far  the  operation  of 
this  mechanism  has  been  considered  as  if  it  were  hand-operated, 
but,  as  a  matter  of  fact,  the  operation  is  automatic.  By  mak- 
ing suitable  adjustment  of  hand-lever  E,  Fig.  6,  at  the  top  of 
the  air  cylinder,  provision  may  be  made  for  either  stopping  the 
machine  or  automatically  reversing  the  direction  of  rotation. 


i6o 


MODERN  DRILLING  PRACTICE 


To  stop  the  machine,  lever  E  is  thrown  down,  and  the  connec- 
tion of  this  lever  with  link  F  and  bellcrank  G  results  in  sliding 
bolt  H  to  the  right.  In  this  position,  cam  /,  attached  to  the 
back  of  rack  C,  comes  down  until  the  flat  bottom  of  this  cam 
engages  bolt  H.  In  this  position,  the  forward  belt  has  been 
shifted  onto  its  loose  pulley,  but  the  reverse  belt  has  not  been 


TO  PIN  ON  TRIP  LEVER 


Machinery 


Fig.  6.     Mechanism  of  Compressed-air  Control  for  Spindle 
Reverse,  shown  in  Place  on  Machine  in  Fig.  5 

shifted  from  its  loose  pulley  to  the  tight  pulley.  As  a  result, 
both  the  forward  and  reverse  belts  are  running  on  their  loose 
pulleys,  and  thus  the  machine  stops. 

If,  on  the  other  hand,  it  is  desired  to  have  the  machine  reverse 
automatically,  lever  E  is  pushed  up  so  that  bolt  H  is  with- 
drawn. It  is  now  possible  for  the  piston  to  descend  right  to  the 
bottom  of  the  air  cylinder,  thus  allowing  the  rack  C  to  shift 
the  "  forward  "  belt  to  its  loose  pulley  and  the  "  reverse  "  belt 


GENERAL  MANUFACTURING  OPERATIONS  161 

to  its  tight  pulley.  This  reverses  the  direction  of  rotation  of  the 
spindle  to  back  out  the  tap.  In  this  position  of  the  mechanism, 
cam  /  descends  and  engages  with  a  corresponding  cam  surface 
on  bellcrank  /,  which  results  in  rocking  this  lever  and  raising 
rod  K.  This  rod  is  connected  to  a  link  mechanism,  which 
drops  the  feed-worm  out  of  engagement  with  the  worm-wheel 
at  the  time  that  the  reverse  belt  is  shifted  onto  the  backward 
driving  pulley.  Under  these  conditions  the  spindle  is  free, 
so  that  the  tap  or  die  can  be  backed  off  the  work.  A  collar 
on  the  drilling  machine  spindle  trips  valve  lever  A  to  provide 
for  reversing  the  machine  at  the  bottom  of  the  spindle  travel, 
i.e.,  when  the  tap  or  threading  die  has  reached  the  desired 
depth;  and  a  second  collar  again  reverses  the  machine  ready 
for  the  next  operation.  To  start  the  machine,  it  is  merely 
necessary  for  the  operator  to  throw  the  feed-worm  into  engage- 
ment with  the  worm-wheel  in  the  usual  way. 

Air  Hose  for  Blowing  away  Chips.  —  Connected  with  the  same 
air  line  that  supplies  the  cylinders  for  reversing  the  direction 
of  rotation  of  the  spindles  for  threading  and  tapping  opera- 
tions, connections  are  made  at  each  machine  with  a  flexible  tube 
and  metal  nozzle,  on  which  there  is  a  push-button  valve. 
This  equipment  is  found  convenient  for  blowing  chips  and  cut- 
ting compound  off  the  work  after  an  operation  has  been  com- 
pleted. It  will  be  seen  that  there  is  a  second  pipe  line  running 
along  at  the  top  of  the  machines,  this  being  provided  to  carry 
cutting  compound  to  the  machine  from  a  single  distributing 
station.  All  bolts  on  the  machine  have  standard  heads  to  fit 
a  single  socket  wrench.  Each  machine  has  its  individual  elec- 
tric light  with  a  shade  which  protects  the  operator's  eyes  and 
directs  all  light  down  to  the  work. 

Electrical  Connections  for  Portable  Tools.  —  At  each  third 
machine,  connection  is  made  with  a  power  circuit,  the  purpose 
of  this  being  to  provide  for  driving  portable  tools.  The  pur- 
pose of  this  is  to  allow  a  portable  drilling  or  tapping  machine 
to  be  brought  into  place  for  performing  one  or  two  operations 
in  cases  where  the  number  of  operations  to  be  performed  is  such 
that  they  cannot  be  conveniently  divided  up  among  the  machines. 


1 62  MODERN  DRILLING  PRACTICE 

When  not  required,  the  portable  machine  is  carried  away  on 
an  elevating  truck;  it  is  mounted  on  a  skid  for  this  purpose. 
At  each  machine  a  safety  plug  is  provided  which  may  be  pulled 
out  to  stop  the  main  driving  motor  in  case  of  emergency. 

Disengagement  of  Feed  for  Facing  Operations.  —  There  are 
a  number  of  different  parts  that  are  machined  on  this  battery 
of  drilling  machines  on  which  it  is  required  to  perform  facing 
operations.  This  work  can  readily  be  handled  on  drilling  ma- 
chines equipped  with  suitable  facing  tools,  but  where  a  fine, 
smooth  finish  is  required  —  as  in  cases  of  couplings  on  gasoline 
pumps,  etc.  —  trouble  would  be  experienced  through  having 
tool-marks  show  on  the  work  if  the  facing  head  were  simply 
advanced  to  the  work  until  the  feed  mechanism  was  tripped 
automatically  and  the  spindle  returned  to  its  upper  position. 
To  overcome  this  trouble,  a  special  equipment  has  been  fur- 
nished on  all  machines,  which  provides  for  disengaging  the 
clutch  at  the  end  of  the  feed-worm  and  still  holding  this  worm 
in  contact  with  the  worm-wheel,  so  that  the  spindle  continues 
to  rotate  with  its  position  held  stationary,  as  far  as  vertical 
feed  movement  is  concerned.  In  this  way,  the  facing  operation 
is  completed  without  any  tool-marks  being  left.  The  same 
device  is  used  to  secure  a  smooth  finish  when  performing  cham- 
fering and  counterboring  operations. 

Two  complete  revolutions  of  the  capstan  wheel  are  necessary 
in  order  to  obtain  the  full  travel  of  the  drill  spindle.  In  work- 
ing out  the  design  of  this  mechanism  for  rotating  a  cutter  without 
any  feed  movement,  while  completing  a  facing  operation,  pro- 
vision had  to  be  made  for  obtaining  practically  the  full  spindle 
travel  to  meet  the  requirement  of  those  cases  where  it  is  neces- 
sary, before  the  feed  is  tripped.  For  this  purpose  the  following 
means  are  employed,  as  shown  in  Figs.  7  and  8.  A  disk  A  is 
bolted  to  the  feed  worm-wheel,  and  this  disk  has  a  circular  T- 
slot  milled  in  it  to  carry  an  adjustable  dog  B.  Pivoted  freely 
on  the  face  of  this  disk  there  is  a  second  member  C  on  which 
there  is  arranged  a  lever  D  that  may  be  pulled  to  advance  a 
catch  E  out  of  the  edge  of  disk  C.  This  catch  E  ultimately 
engages  the  upper  end  of  a  bellcrank  lever  (the  lower  end  of 


GENERAL  MANUFACTURING  OPERATIONS 


which  is  shown  at  F)  which  results  in  causing  the  lower  end  of 

this  lever  to  disengage  the  clutch  at  the  end  of  the  feed-worm 

shaft.     Just  how  the  mechanism  operates  will  now  be  described. 

In  operation,  the  position  of  dog  B  is  adjusted  in  the  cir- 


m 


Fig.  7.     Close  View  of  Mechanism  employed  to  Disengage  Feed 
but  hold  Spindle  Vertically  while  completing  Facing  Operations 

cular  T-slot  in  disk  A,  so  that  this  dog  causes  catch  E  to  trip 
the  feed-worm  clutch  when  the  spindle  has  reached  the  desired 
position.  As  two  complete  revolutions  of  the  capstan  wheel 
are  required  to  secure  the  maximum  feed  motion  for  the  spindle, 
it  was  necessary  to  employ  the  double  arrangement  of  disks 


1 64  MODERN  DRILLING  PRACTICE 

shown  at  A  and  C,  in  order  that  disk  A  can  make  a  complete 
revolution  to  bring  dog  B  to  the  opposite  side  of  the  lug  on 
disk  C,  after  which  continued  revolution  of  disk  A  causes  dog  B 
to  carry  disk  C  around.  When  this  revolution  has  been  com- 
pleted,  catch  E  engages  bellcrank  lever  F  and  trips  the  feed- 
worm.  Of  course,  any  portion  of  the  maximum  feed  movement 
of  the  drill  spindle  may  be  obtained  by  making  a  proper  setting 
of  dog  B. 

When  the  clutch  has  been  disengaged  on  the  feed-worm 
shaft,  it  will  be  apparent  that  the  worm  is  still  in  engagement 
with  the  worm-wheel,  which  prevents  the  counterweight  from 
returning  the  spindle;  at  the  same  time,  the  spindle  continues 
to  rotate,  thus  completing  the  facing  operation  with  a  fixed 
vertical  position  of  the  cutter,  so  that  the  work  is  finished  with- 
out showing  any  tool-marks.  To  complete  the  cycle  of  opera- 
tions, it  will  be  apparent  that  the  feed-worm  must  be  thrown 
out  of  engagement  with  the  worm-wheel  so  that  the  spindle 
may  be  returned  to  the  starting  position.  The  mechanism 
provides  means  of  doing  this  automatically,  the  operation  being 
as  follows:  The  preceding  description  has  explained  how  catch 
E  comes  into  contact  with  bellcrank  F  and  results  in  disen- 
gaging the  clutch  on  the  feed-worm  shaft.  After  this  has  been 
done,  it  is  necessary  for  pinion  H  to  be  brought  into  mesh  with 
gear  /  in  order  that  a  dog  mounted  in  one  of  the  holes  /  in  gear 
/  may  engage  with  a  link  to  throw  the  feed- worm  out  of  engage- 
ment with  the  worm-wheel. 

After  catch  E  has  engaged  with  bellcrank  lever  F  and  moved 
this  lever  sufficiently  to  disengage  the  clutch  on  the  feed-worm 
shaft,  catch  E  plays  no  further  part  in  the  operation.  Carried 
by  lever  G  there  is  a  spring  plunger  with  a  roller  at  its  end, 
which  runs  over  the  V-shaped  block  secured  to  the  frame  of  the 
machine.  At  the  same  moment  that  catch  E  has  disengaged 
the  feed-clutch,  this  roller  carried  by  the  spring  plunger  on 
lever  G  has  reached  the  position  at  the  apex  of  the  V-shaped 
block.  The  spring  behind  the  plunger  is  now  compressed  so 
that  its  maximum  tension  is  exerted,  and  as  the  roller  passes 
over  the  top  of  the  vee,  the  spring  pressure  becomes  effective 


GENERAL  MANUFACTURING  OPERATIONS 


in  causing  the  roller  to  run  down  the  decline  of  the  V-shaped 
block.  In  so  doing,  a  further  movement  is  imparted  to  lever  G 
which  has  the  following  effect:  Pinion  H  is  carried  on  a  quad- 
rant, which  has  been  gradually  swung  over  during  the  time  that 


Fig.  8.     Another  View  of  Mechanism  shown  in  Fig.  7 

catch  E  is  in  contact  with  bellcrank  F.  As  the  roller  carried 
by  the  spring  plunger  on  lever  G  runs  down  the  decline  of  the  V- 
block,  movement  imparted  to  lever  G  is  transmitted  through  a 
link  mechanism  of  which  M  is  a  part,  which  results  in  bringing 
pinion  H  into  mesh  with  gear  /. 


1 66  MODERN  DRILLING  PRACTICE 

As  previously  mentioned,  a  pin  carried  in  one  of  the  holes 
in  this  gear  trips  the  feed-worm  out  of  engagement  with  the 
worm-wheel.  The  counterweight  then  returns  the  spindle  to 
its  upper  position.  At  this  point  collar  N  carried  by  the 
spindle  engages  lever  0,  which  imparts  the  reverse  movement 
to  the  mechanism  which  has  just  been  described.  In  the  first 
place,  the  quadrant  which  carries  pinion  H  is  rocked  back  so 
that  this  pinion  is  disengaged  from  gear  7.  Gear  I  is  made 
heavy  at  what  is  the  lower  side  in  the  starting  position,  and 
this  gear  is  free  on  its  shaft,  so  that,  when  the  pinion  is  dis- 
engaged, gear  /  is  automatically  returned  to  the  starting  posi- 
tion, where  the  heavy  side  of  the  gear  is  at  the  bottom.  Bell- 
crank  lever  F  and  the  .extension  G  of  this  bellcrank  are  also 
returned  to  their  starting  positions  ready  for  the  next  cycle  of 
operations.  When  the  operator  has  set  up  the  next  piece  of 
work,  he  merely  has  to  engage  the  feed-worm  with  the  wheel, 
after  which  he  goes  on  to  the  next  machine. 

Drilling  Machine  equipped  for  Milling  Operation.  —  Im- 
provements which  have  been  made  in  the  design  of  drilling 
machines,  and  a  better  understanding  of  the  possibilities  of 
these  machines  by  shop  superintendents  and  others  who  decide 
upon  methods  of  performing  machining  operations,  have  led  to 
a  remarkable  extension  of  the  range  of  work  handled  on  this 
type  of  machine  tools. 

In  Fig.  9  is  shown  the  way  in  which  the  Rockford  Drilling 
Machine  Co.,  Rockford,  111.,  has  equipped  a  high-duty  drilling 
machine  of  its  manufacture  for  use  in  milling  universal  joint 
rings.  It  will  be  apparent  from  this  illustration  that  the  work- 
holding  fixture  is  so  designed  that  the  operation  is  conducted 
on  what  is  commonly  known  as  the  "  continuous  "  principle; 
that  is,  the  fixture  revolves  so  that  forgings  are  constantly  being 
fed  under  the  milling  cutter,  and  the  operator  has  plenty  of  time 
to  remove  the  milled  universal  joint  rings  from  the  fixture  and 
substitute  rough  forgings.  These  forgings  are  made  of  0.25  per 
cent  carbon  steel  and  are  held  in  place  on  the  fixture  by  means  of 
T-clamps.  The  drilling  machine  used  for  this  work  is  equipped 
with  a  special  spindle  of  suitable  design  for  driving  the  large 


GENERAL  MANUFACTURING  OPERATIONS  167 

inserted-tooth  face  milling  cutter,  which  can  just  be  seen  pro- 
jecting down  below  the  guard  that  is  furnished  to  protect  the 
operator  against  injury. 


Fig.  9.     Drilling  Machine  equipped  with  Continuous  Milling  Fixture 
for  Milling  Universal  Joint  Rings 

Broaching  Operation  on  Drilling  Machine.  —  Regardless  of 
the  views  held  by  any  man  who  plans  methods  of  performing 
machining  operations  concerning  what  constitutes  drilling  ma- 
chine work,  there  are  few  of  these  men  who  will  not  concede 
that  the  use  of  a  drilling  machine  for  simultaneously  broaching 
eight  slots  is  somewhat  unusual.  Fig.  10  shows  the  way  in 


II  G 


i68 


MODERN  DRILLING  PRACTICE 


which  the  Willys-Overland  Co.,  of  Toledo,  Ohio,  has  equipped  a 
42-inch  reversing  type  of  drilling  machine,  built  by  the  Cin- 
cinnati Machine  Tool  Co.,  Cincinnati,  Ohio,  for  broaching  eight 
slots  in  an  aluminum  crankcase  to  receive  the  push-rod  guides, 


Fig.  10.     Reversing  Drilling  Machine  equipped  for  Broaching 
Push-rod  Guide  Slots  in  Crankcases 

all  of  this  work  being  finished  by  one  feed  movement  of  the  drill- 
ing machine  spindle.  For  the  performance  of  this  operation, 
the  work  is  located  by  plugs  on  the  fixture  which  enter  the 
camshaft  bearing  holes  at  each  end  of  the  crankcase.  Carried 
by  the  main  spindle  of  the  drilling  machine  there  is  a  pinion 


GENERAL  MANUFACTURING  OPERATIONS  169 

which  drives  two  gears  carried  in  cases  A.  These  gears  are 
threaded  onto  screws  B,  the  pitch  of  which  is  such  that,  as  the 
gears  are  turned,  they  feed  down  the  holder  carrying  the  eight 
broaches  C  at  the  same  rate  that  the  drilling  machine  spindle 
carries  down  the  driving  pinion.  When  the  broaches  have 
reached  the  bottom  of  their  downward  stroke,  lever  D  is  manipu- 
lated to  reverse  the  direction  of  rotation  of  the  drilling  machine 
spindle,  which  results  in  backing  out  the  broaches.  The 
broaches  are  fed  into  the  work  at  the  rate  of  12  inches  per  min- 
ute, with  a  feed  of  0.006  inch  per  tooth,  and  with  this  equipment 
1 20  crankcases  are  broached  per  hour. 

Driving  Studs  by  Power.  —  The  Errington  Mechanical  Labo- 
ratory, New  York  City,  makes  a  stud  setter  of  the  type  which 
opens  automatically.  It  is  equipped  with  two  threaded  jaws  or 
half-nuts  which  are  released  and  open,  after  the  stud  is  set, 
in  practically  the  same  way  that  an  automatic  die  opens  at 
the  end  of  a  cut.  The  opening  of  the  stud  setter  is  controlled 
by  a  stop-collar  which  is  placed  around  the  stud.  When  the 
lower  end  of  the  stud  setter  engages  this  collar,  the  body  of 
the  stud  setter  is  prevented  from  further  downward  move- 
ment, but,  as  it  continues  to  revolve,  the  two  jaws  or  half- 
nuts  screw  themselves  onto  the  stud  until  a  collar  at  the  lower 
end  moves  down  opposite  a  recess  or  counterbored  part  of  the 
stud-setter  body.  As  this  collar  normally  supports  the  half- 
nuts,  they  are  released  when  the  supporting  collar  enters  the 
enlarged  part  of  the  stud-setter  body.  The  entire  tool  is  then 
raised  as  it  continues  to  revolve  in  the  same  direction  as  for 
driving  in  the  stud.  The  half-nuts  are  reset  for  the  next  stud 
by  sliding  another  collar  upward.  This  collar  is  recessed  on  the 
inside  and  engages  the  projecting  ends  of  pins  connected  with 
the  jaws  or  half-nuts,  and  simply  serves  to  move  them  upward 
so  that  the  supporting  collar  will  be  caused  to  enter  the  smaller 
bore  of  the  stud-setter  body  and  once  more  close  the  jaws  ready 
to  engage  the  next  stud.  This  tool  may  be  rotated  either  in  a 
drilling  machine  or  by  means  of  a  portable  pneumatic  or  electric 
drill.  Flexible  shafting  is  also  used  in  some  cases.  The  gen- 
eral method  of  setting  studs  is  to  start  them  by  hand  and  then 


i  yo 


MODERN  DRILLING  PRACTICE 


drive  them  in  by  power.  If  a  stud  is  too  tight  and  requires  an 
unusual  amount  of  power  for  driving  it,  the  stud  setter  can  be 
released  at  any  time  by  simply  raising  the  machine  spindle,  as 


Fig.  ii.     Stud  Setter  operated  by  Vertical  Drilling  Machine 

this  moves  the  outer  shell  of  the  stud-setter  body  upward  and 
brings  the  half-nuts  into  the  releasing  position.  Fig.  n  shows 
one  of  these  Errington  stud  setters  being  driven  by  a  drilling 
machine. 


GENERAL  MANUFACTURING  OPERATIONS 


171 


Assembling  with  Drilling  Machine.  —  A  large  part  of  the 
labor  of  assembling  machine  parts  that  are  held  together  by 
screws,  bolts,  and  nuts  is  spent  in  the  act  of  screwing  the  parts 
together  with  a  wrench.  When  a  nut  is  started  on  a  screw 


Fig.  12.     Drilling  Machine  used  for  Assembling  Universal  Joints 

thread,  there  is  no  reason  why  manual  power  should  be  employed 
to  screw  it  in,  provided  there  are  a  sufficient  number  of  one 
size  to  warrant  the  use  of  power  apparatus.  In  the  manufacture 
of  motor  cars,  special  appliances  are  employed  for  assembling, 


172 


MODERN  DRILLING  PRACTICE 


especially  for  setting  studs  and  screwing  up  nuts.  In  some 
cases,  as  many  as  sixteen  nuts  are  driven  in  simultaneously  by 
multiple-spindle  drilling  machine  attachments.  While  it  is 
necessary  for  the  operator  to  test  each  nut  with  a  wrench  to  see 
that  it  is  screwed  in  firmly,  the  power  apparatus  saves  a  great 
deal  of  time  and  strength.  However,  the  use  of  power  appa- 


Machinery 


Fig.  13.     Fixture  for  Assembling  Universal  Joint  Rings  on  Drilling 
Machine  as  shown  in  Fig.  12 

ratus  for  setting  studs  and  screwing  up  nuts  is  not  necessarily 
confined  to  the  manufacture  of  machinery  built  in  large  quan- 
tities. It  is  quite  feasible  to  employ  an  ordinary  single-spindle 
drilling  machine  effectively  for  assembling  simple  parts  that  are 
made  in  quantities,  especially  if  they  have  a  number  of  nuts 
of  the  same  size  that  may  be  screwed  up  consecutively  during 
one  operation.  The  drilling  machine  may  be  used  as  an  assem- 
bling machine  in  many  plants  where  the  idea  has  never  been 
employed  or  even  suggested. 


GENERAL   MANUFACTURING  OPERATIONS  173 

Fig.  12  shows  a  drilling  machine  built  by  the  Rockford  Drill- 
ing Machine  Co.,  Rockford,  111.,  which  is  used  in  this  company's 
plant  for  tightening  the  four  nuts  on  the  bolts  that  hold  to- 


Fig.  14.     Pneumatic  Drill  screwing  in  Cap-screws 

gether  the  parts  of  a  motor  car  universal  joint  assembly.  The 
universal  joint  is  mounted  in  a  fixture  of  the  form  shown  in 
Fig.  13,  which  holds  the  ring  level  and  thus  presents  the  nuts 
to  be  tightened  in  a  horizontal  plane.  The  operator  starts  the 
nuts  on  the  screws  by  hand,  having  all  four  nuts  ready  before 


174 


MODERN  DRILLING  PRACTICE 


placing  the  joint  in  the  fixture  for  screwing  them  down.  The 
wrench  carried  by  the  drilling  machine  spindle  is  then  applied 
and  the  nut  is  screwed  up  as  far  as  it  will  go  or  until  the  bolt 
slips.  After  this  has  been  done,  the  fixture  is  indexed  to  the 


Fig.  15.     Tools  and  Work-holding  Fixture  for  Forming  Bevel 
Gear  Blanks  on  High-duty  Drilling  Machine 

next  position  and  the  operation  repeated.  The  fixture  is  essen- 
tially simple,  consisting  of  a  base  that  is  bored  and  faced  to 
receive  the  member  on  which  the  universal  joints  rest.  A 
hardened  steel  ball  and  a  coiled  spring  seated  in  a  hole  in  the 
base  constitute  the  indexing  and  locating  plunger.  It  offers 


GENERAL  MANUFACTURING  OPERATIONS 


175 


sufficient  resistance  to  hold  the  fixture  in  place,  but  not  enough 
to  prevent  the  operator  from  easily  turning  the  indexing  mem- 
ber of  the  fixture  around  to  the  next  station. 

Fig.  14  shows  another  method  of  employing  a  power-driven 
machine  to  assist  in  the  rapid  assembling  of  machine  parts. 
Here  there  is  shown  a  No.  33  "  Little  David  "  portable  pneu- 
matic drilling  machine  made  by  the  Ingersoll-Rand  Co.,  New 
York  City,  which  is  used  in  the  plant  of  the  H.  H.  Franklin 
Mfg.  Co.,  Syracuse,  N.  Y.,  for  "  running  in  "  cap-screws.  The 


0 


o  I       frri       1  rrn 


Machinery 


Fig.  1 6.     Sectional  View  of  Tool  and  Work-holding  Fixture 
shown  in  Fig.  15 

pneumatic  drill  is  suspended  in  such  a  way  that  the  operator  is 
relieved  as  far  as  possible  from  the  work  of  lifting  the  tool.  In 
this  way,  the  fatigue  factor  is  reduced  to  a  minimum,  enabling 
the  operator's  efficiency  to  remain  as  nearly  normal  as  possible 
during  the  entire  working  day.  The  speed  at  which  cap-screws 
may  be  run  in  by  this  method,  as  compared  with  the  laborious 
method  of  driving  them  by  hand,  will  be  quite  obvious. 

Forming  Operation  on  a  Drilling  Machine.  —  A  somewhat 
unusual  way  of  performing  a  forming  operation  will  be  seen  in 
Figs.  15  and  16,  which  show  the  tools  and  work-holding  fixtures 


176  MODERN  DRILLING  PRACTICE 

provided  for  turning  up  bevel  gear  blanks  from  steel  forgings. 
For  handling  this  work,  the  order  of  operations  is  as  follows: 
First,  drill  a  hole  through  the  center  of  a  blank;  second,  cut  a 
keyseat  in  the  blank;  third,  locate  the  work  on  the  piloted 
fixture  and  form  one  side  of  the  blank;  fourth,  turn  the  work 
over  and  form  the  opposite  side  of  the  blank.  In  the  first 
forming  operation,  the  face  of  the  gear  blank  is  formed  by  tool 
A  (Fig.  15);  tool  B  cuts  the  recess,  and  tool  C  cuts  away  the 
excess  metal  to  reduce  the  gear  blank  to  the  required  outside 
diameter.  After  this  operation  has  been  completed  on  all  of 
the  gear  blanks,  the  tools  are  changed  and  the  work  is  turned 
over  so  that  the  opposite  side  of  the  blank  may  be  turned  to  the 
desired  form,  which  is  indicated  by  the  cross-sectional  view  in 
Fig.  1 6.  As  the  gear  blanks  are  turned  from  steel  forgings, 
evidently  a  high-duty  machine  is  required  to  handle  severe 
service  of  this  kind.  The  pilot  D  on  the  work-holding  fixture 
extends  up  into  a  bushing  E  in  the  tool  to  eliminate  all  chance  of 
springing  the  tool  away  from  the  cut.  The  work  is  shown  in 
the  course  of  production  on  a  No.  314  high-duty  drilling  ma- 
chine built  by  Baker  Bros.,  Toledo,  Ohio,  and  the  gear  blanks 
being  turned  are  for  the  bevel  gear  drive  on  these  machines. 


CHAPTER  ix 

JIGS,   FIXTURES,   AND   SPECIAL  TOOLS  FOR 
DRILLING   MACHINES 

A  JIG  or  work-holding  fixture  may  be  used  on  a  drilling  ma- 
chine to  provide  for  interchangeability  of  the  drilled  pieces, 
or  it  may  be  used  for  the  sole  purpose  of  holding  the  work  and 
preventing  it  from  turning  while  the  drilling  operation  is  being 
performed.  By  far,  the  most  important  object  of  using  a  jig  or 
fixture  for  drilling  parts  that  are  to  be  assembled  together  is 
to  eliminate  laying  out  work  and  to  provide  for  accurately  lo- 
cating holes  in  all  duplicate  parts  produced  on  the  drilling 
machine,  so  that  bolts,  screws,  etc.,  will  enter  holes  in  all  of 
these  parts  without  the  necessity  of  subsequent  hand  fitting. 
Obviously,  the  use  of  jigs  and  fixtures  provides  means  of  greatly 
reducing  the  ultimate  cost  of  producing  such  parts.  A  further 
economy  is  secured  through  their  use,  owing  to  the  fact  that 
both  the  jig  or  fixture  and  the  drilling  machine  can  be  made  so 
simple  to  operate  that  unskilled  labor  may  be  employed  with 
assurance  that  the  work  will  possess  the  desired  degree  of  ac- 
curacy. Aside  from  the  actual  saving  in  the  cost  of  performing 
drilling  operations,  it  is  obvious  that  an  even  greater  saving  will 
usually  be  effected  through  the  production  of  interchangeable 
parts  which  may  be  sent  directly  to  the  assembling  department, 
where  they  are  ready  to  be  assembled  into  the  finished  product 
without  requiring  any  hand  work.  Still  another  claim  in  favor 
of  the  use  of  jigs  and  fixtures  is  that  the  production  of  inter- 
changeable parts  makes  it  a  very  simple  matter  for  broken 
pieces  to  be  replaced,  with  perfect  assurance  that  such  pieces 
will  fit  properly  when  received  by  the  customer. 

In  practically  all  up-to-date  manufacturing  establishments, 
interchangeable  manufacture  is  now  in  use  and  one  of  the  great 
advantages  of  this  system  is  that,  where  a  complete  equip- 
ment of  jigs  and  fixtures  is  employed  for  the  performance  of 
all  machining  operations,  work  may  continue  on  the  produc- 

177 


178  MODERN  DRILLING  PRACTICE 

tion  of  all  different  parts  of  the  product  which  are  machined 
in  different  departments  of  the  factory  with  assurance  that 
these  parts  will  assemble  together  properly.  This  saves  the 
necessity  of  waiting  for  one  part  to  be  finished  so  that  other 
parts  may  be  fitted  to  it,  as  was  the  case  under  the  old  method 
of  "  building  "  a  machine,  which  stands  out  in  strong  contradis- 
tinction to  the  modern  methods  of  "  manufacturing  "  which  are 
now  employed.  Necessarily,  the  attainment  of  this  result  calls 
for  the  use  of  a  set  of  jigs  and  fixtures  which  have  been  very 
carefully  designed  so  that  the  relation  of  all  machined  holes 
and  surfaces  is  not  only  accurate  in  a  given  piece,  but  is 
also  accurate  in  relation  to  each  other. 

The  terms  "  jig  "  and  "  fixture  "  are  often  applied  to  the  same 
class  of  equipment,  although  there  is  a  distinction  between  these 
terms.  Jigs  and  fixtures  are  made  in  such  a  great  variety  of 
types  that  it  is  hard  to  cover  the  subject  comprehensively  with- 
out going  into  a  great  deal  of  detail.  Probably  the  best  general 
distinction  to  make  is  that  a  jig  is  furnished  with  hardened 
steel  bushings,  through  which  the  drills  are  guided  into  the  work, 
while  in  the  case  of  a  fixture  the  desired  location  is  secured 
through  the  provision  of  gage  points  on  the  fixture  or  by  some 
other  means.  A  combination  of  gage  points  and  bushings  is 
often  employed  in  working  out  the  design  of  a  jig.  In  both  jigs 
and  fixtures,  provision  is  commonly  made  for  holding  the  work 
to  prevent  it  from  turning,  although  there  are  special  cases 
where  jigs  are  clamped  to  the  work  or  dropped  over  a  machined 
surface  which  affords  the  desired  location  for  the  jig.  In  the 
majority  of  cases,  however,  both  jigs  and  fixtures  are  furnished 
with  means  of  securing  them  to  the  table  of  the  drilling  machine, 
common  methods  of  obtaining  this  result  being  to  provide  a 
tongue  on  the  bottom  of  the  fixture  which  enters  a  T-slot  in 
the  table,  or  to  employ  some  similar  method. 

Essential  Features  of  Jig  Design.  —  In  working  out  the  de- 
sign of  either  jigs  or  fixtures,  there  are  a  number  of  points  which 
must  receive  careful  consideration  if  the  most  satisfactory  results 
are  to  be  obtained.  Among  these  there  is  none  of  greater 
importance  than  to  be  sure  that  the  design  of  clamping  devices 


JIGS,  FIXTURES,  AND   SPECIAL  TOOLS  179 

which  are  furnished  to  secure  the  work  in  place  and  the  form  of 
the  fixture  are  both  such  that  the  work  may  be  put  in  and  taken 
out  after  the  drilling  operation  has  been  completed  without 
entailing  an  unnecessary  loss  of  time.  This  point  has  assumed 
exceptional  importance  on  account  of  the  steadily  increasing 
rates  of  speed  and  feed  employed  in  the  performance  of  drilling 
operations,  because  the  consequent  reduction  in  drilling  time 
means  that  the  ratio  of  setting-up  time  to  drilling  time  will 
become  constantly  less  favorable  unless  great  care  is  taken  to 
eliminate  all  unnecessary  loss  in  setting  up  the  work.  Generally 
speaking,  it  is  necessary  to  provide  a  jig  or  fixture  for  use  in 
drilling  the  hole  in  a  part  which  is  to  be  assembled  with  a  second 
part  that  has  been  drilled  with  the  use  of  similar  equipment. 
There  are  certain  cases,  however,  where  this  is  not  advisable, 
as  it  may  be  impossible  to  properly  locate  a  jig  on  one  of  the 
parts  to  be  drilled,  or  if  the  attempt  were  made  to  design  a  jig, 
it  would  be  so  complicated  as  to  prove  impractical.  In  such 
cases,  the  part  drilled  in  a  jig  is  used  as  the  jig  for  drilling  the 
second  part  on  which  it  is  to  be  assembled,  and,  where  this 
method  is  followed,  satisfactory  results  are  secured,  although 
the  production  time  is  likely  to  appear  somewhat  high. 

One  of  the  most  important  questions  that  should  be  decided 
before  making  a  jig  is  the  amount  of  money  that  can  be  profit- 
ably spent  on  special  tools  for  the  operation  under  consideration. 
In  many  cases  greater  efficiency  could  be  secured  by  making  a 
complicated  and  expensive  tool,  but  this  additional  investment 
would  not  be  warranted  by  the  slight  saving  in  production  cost 
that  would  be  effected  through  its  use.  In  all  cases  where  the 
question  of  jig  and  fixture  design  comes  up,  a  careful  comparison 
should  be  made  of  the  cost  of  drilling  under  the  present  method 
and  the  estimated  cost  of  performing  the  same  operation  in  the 
new  jig  or  fixture ;  and  unless  the  saving  is  sufficient  to  warrant 
adoption  of  the  new  method,  it  is  obvious  that  further  work 
should  be  done  by  the  tool  designer  to  see  if  a  greater  reduction 
in  production  cost  is  not  possible.  While  discussing  the  question 
of  cost,  attention  is  called  to  the  fairly  obvious  fact  that  the 
number  of  parts  to  be  machined  will  determine  the  expenditure 


l8o  MODERN  DRILLING  PRACTICE 

that  is  warranted  for  jigs  and  fixtures,  as  it  would  be  obviously 
impractical  to  spend  a  lot  of  money  for  special  work-holding 
equipment  —  regardless  of  the  efficient  results  that  could  be 
secured  through  its  use  —  unless  the  number  of  parts  to  be 
drilled  were  great  enough  to  return  a  satisfactory  income  on  the 
tool  investment. 

Selection  of  Locating  Points.  —  In  choosing  the  locating  sur- 
face of  gage  points  on  the  work  to  be  drilled,  consideration 
must  be  given  to  the  facilities  for  locating  the  corresponding 
part  with  which  it  is  to  be  assembled.  This  is  a  highly  impor- 
tant point,  because,  although  jigs  may  be  alike  as  far  as  their 
provision  for  locating  the  holes  is  concerned,  there  may  be  no 
facility  for  locating  holes  in  the  corresponding  part  in  the  same 
manner  that  was  used  in  the  one  for  which  a  satisfactory  selec- 
tion of  locating  points  was  made.  In  such  cases,  while  the 
drilled  holes  may  coincide,  other  surfaces  which  are  required  to 
come  into  coincidence  may  be  considerably  out  of  line.  There- 
fore, one  of  the  main  principles  of  location  is  to  have  the  two 
component  parts  located  from  corresponding  points  or  surfaces 
on  the  castings.  This  naturally  draws  attention  to  the  im- 
portance of  designing  patterns  for  use  in  the  foundry  with  suit- 
able provision  for  holding  the  castings  while  they  are  being 
drilled.  It  is  sometimes  apparent  that  lack  of  cooperation  be- 
tween the  drafting-room  and  machine  shop,  which  results  in 
failure  to  provide  efficient  means  for  holding  the  work,  is  re- 
sponsible for  adding  greatly  to  the  cost  of  performing  machin- 
ing operations. 

Wherever  it  is  possible,  special  arrangements  should  be  made 
in  designing  jigs  and  fixtures  so  that  it  is  impossible  to  insert 
the  piece  in  any  but  the  correct  way.  This  is  especially  impor- 
tant in  developing  tools  for  use  in  those  shops  where  a  great 
deal  of  unskilled  labor  is  employed,  as  care  taken  by  the  tool 
designers  will  often  be  the  means  of  saving  a  great  deal  of  money 
which  would  be  lost  through  spoiling  work.  The  use  of  "  fool- 
proof "  jigs  and  fixtures  in  which  it  is  impossible  to  insert  the 
work  upside  down,  etc.,  will  also  be  the  means  of  making  impor- 
tant savings  in  plants  where  the  labor  is  fairly  well  trained  in  the 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS  181 

performance  of  the  different  classes  of  work,  but  where  the  use 
of  a  piece-work  system  may  be  responsible  for  some  slight 
carelessness  on  the  part  of  machine  operators.  Another  im- 
portant point  is  that  where  the  work  may  vary  in  size,  as  in  the 
case  of  rough  castings,  etc.,  it  is  necessary  to  have  at  least  some 
of  the  locating  points  made  adjustable  and  placed  so  that  they 
can  be  easily  reached  to  make  the  necessary  adjustment,  and 
then  fastened  so  that  they  are  reasonably  positive  in  their 
function  of  locating  the  work. 

Clamping  Devices.  —  In  designing  clamping  devices,  care 
should  be  taken  to  arrange  each  clamp  so  that  the  direction  in 
which  the  strain  of  the  tool  or  cutter  acts  upon  the  work  is  such 
that  the  clamp  will  possess  the  maximum  strength  to  resist  the 
pressure  of  the  cut.  Another  important  point  is  to  design  the 
clamps  so  that  they  may  not  readily  be  detached  from  the 
fixture  and  require  a  lot  of  time  to  be  spent  in  finding  cla'mps 
which  have  been  mislaid.  In  all  cases,  clamping  devices  should 
be  made  as  simple  as  possible  and  they  should  be  made  to  operate 
quickly  for  reasons  that  have  already  been  mentioned.  In 
addition  to  designing  clamps  so  that  they  are  strong  enough  to 
resist  the  pressure  of  the  cut,  it  is  highly  important  to  see  that 
such  pressure  will  not  result  in  springing  the  work  out  of  place 
and  cause  inaccuracy  in  the  location  of  holes  and  machined 
surfaces.  This  point  can  best  be  taken  care  of  by  paying  at- 
tention to  the  selection  of  locating  and  bearing  points  for  the 
work  and  clamps,  respectively,  so  that  the  probability  of  spring- 
ing the  work  is  reduced  as  far  as  possible.  One  point  to  observe 
in  providing  for  rigidity  is  to  locate  clamps  or  straps  so  that 
they  are  exactly  opposite  some  bearing  point  on  the  surface  of 
the  work,  whenever  such  a  location  is  found  feasible.  Another 
point  of  importance,  in  so  far  as  it  may  affect  the  accuracy  of 
work  produced  in  a  jig  or  fixture,  is  to  work  out  the  design  in 
such  a  way  that  chips  may  be  readily  cleared  out  of  the  fixture 
to  avoid  danger  of  inaccuracy  resulting  from  chips  accumulating 
on  the  locating  points. 

Jigs  and  fixtures  should  be  made  as  light  as  possible  in  order 
that  they  may  be  easily  handled.  One  way  of  securing  this 


182  MODERN  DRILLING  PRACTICE 

result  is  to  design  the  castings  with  cored  holes  wherever  metal 
may  be  eliminated  without  unduly  affecting  the  strength  of  the 
tool.  Where  jigs  are  provided  with  feet,  some  designers  favor 
the  use  of  three  feet,  because  with  such  an  arrangement  they 
are  always  sure  of  the  jig  taking  a  firm  bearing  on  the  machine 
table.  As  a  matter  of  fact,  this  is  an  undesirable  form  of  design, 
because  there  is  nothing  to  show  the  presence  of  chips  or  other 
foreign  matter  under  one  of  the  feet  of  the  jig  or  fixture,  which 
would  cause  inaccuracy  in  the  setting  of  the  work.  With  a 
design  in  which  four  feet  are  provided,  the  presence  of  anything 
under  one  of  the  feet  will  immediately  be  shown  by  the  fact 
that  an  improper  bearing  is  provided  and  the  jig  will  tend  to 
rock  in  an  unsteady  manner  until  the  trouble  has  been  corrected. 

Materials  used  in  Making  Jigs  and  Fixtures.  —  Opinion 
differs  as  to  the  relative  merits  of  cast  iron  and  steel  for  use  in 
making  the  bodies  of  jigs  and  fixtures.  In  deciding  this  point, 
attention  should  be  given  to  the  use  to  which  the  tool  is  to  be 
put  and  the  character  of  the  work  which  it  is  to  handle.  It  is 
difficult  to  make  a  general  statement,  but  the  best  opinion 
seems  to  be  that  for  small  and  medium  sized  work,  such  as 
parts  of  sewing  machines,  typewriters,  adding  machines,  cash 
registers,  phonographs,  guns,  etc.,  the- steel  jig  offers  decided 
advantages;  but  in  the  case  of  large  work  of  the  kind  that 
has  to  be  machined  in  factories  engaged  in  the  manufacture 
of  machine  tools,  engines,  and  automobiles,  cast  iron  is  un- 
doubtedly the  cheaper  and  more  satisfactory  material. 

Summary  of  Important  Points  in  Design  of  Jigs  and  Fixtures. 
—  In  presenting  the  following  summary  of  the  features  which 
should  be  provided  in  designing  jigs  and  fixtures,  the  idea  is 
to  furnish  data  which  the  tool  designer  may  run  over  in  check- 
ing up  his  design.  Experienced  men  will  not  find  it  necessary 
to  take  such  precautions,  but  in  the  case  of  designers  who  have 
not  had  an  opportunity  to  gain  the  necessary  experience  to 
make  their  judgment  absolutely  reliable,  checking  over  a  design 
to  see  that  it  meets  the  following  requirements  will  often  be  the 
means  of  saving  costly  mistakes.  These  requirements  may  be 
briefly  summarized  as  follows: 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS  183 

(A)  Does  the  estimated  production  cost  of  drilling  work  in 
the  new  jigs  and  fixtures  show  sufficient  saving  over  the  cost 
with  existing  tool  equipment  to  warrant  ordering  new  tools? 
(B)  Were  locating  points  selected  and  the  method  of  clamping 
decided  upon  before  laying  out  the  jig  or  fixture?  (C)  Have  all 
clamping  devices  been  made  as  quick-acting  as  possible?  (D) 
Were  locating  points  for  use  in  machining  component  parts 
selected  on  corresponding  surfaces  on  these  parts?  (E)  Has 
the  jig  or  fixture  been  made  fool-proof,  i.e.,  is  it  arranged  so 
that  work  cannot  be  inserted  except  in  the  correct  way?  (F) 
If  the  jig  is  used  for  holding  rough  castings,  has  adjustment 
been  provided  for  the  locating  points  to  compensate  for  varia- 
tions in  the  size  of  the  castings?  (G)  Are  all  clamps  located  in 
the  best  position  to  resist  pressure  of  cutting  tool?  (H)  Have 
all  clamps  been  made  integral  parts  of  the  jig  or  fixture  where 
possible?  (I)  Has  the  design  of  the  clamping  mechanism  been 
simplified  as  far  as  possible?  (J)  Has  provision  to  avoid  spring- 
ing the  work  been  made  by  placing  all  clamps  as  nearly  as 
possible  opposite  to  bearing  points  on  the  work?  (K)  Has  the 
jig  or  fixture  been  made  as  light  as  is  consistent  with  rigidity 
and  stiffness  by  coring  out  unnecessary  metal?  (L)  Have  all 
corners  been  made  round?  (M)  Have  handles  been  provided 
where  these  will  make  handling  of  the  jig  or  fixture  more  easily 
accomplished?  (N)  Has  adequate  support  been  provided  by 
placing  feet,  etc.,  directly  beneath  all  points  where  the  pressure 
of  cut  will  come?  (0)  Has  ample  clearance  been  provided  in 
jigs  or  fixtures  used  for  drilling  rough  castings?  (P)  Have  all 
locating  points  been  made  visible  to  the  operator  while  placing 
work  in  position  in  the  jig  or  fixture?  (Q)  Have  holes  been 
provided  for  the  removal  of  chips  from  the  jig  or  fixture?  (R) 
Have  clamping  lugs  been  located  in  such  a  way  as  to  prevent 
springing  the  fixture  in  cases  where  the  fixture  must  be  secured 
to  the  drilling  machine  table?  (S)  Have  instructions  been 
given  for  the  jig  or  fixture  to  be  tested  before  it  is  sent  to  the 
shop  to  be  used? 

Types  of  Jigs  and  Fixtures.  —  The  variety  of  different  jigs 
and  fixtures  which  are  in  use  at  the  present  time  is  so  great  that 


184  MODERN  DRILLING  PRACTICE 

the  scope  of  an  article  of  this  kind  does  not  include  complete 
discussion.  At  the  same  time,  the  principles  which  have  just 
been  enunciated  apply  to  all  of  these  different  types,  and  if 
carefully  followed  will  be  the  means  of  greatly  improving  the 
efficiency  of  results  secured  with  the  auxiliary  equipment  de- 
signed for  use  on  the  drilling  machines.  Briefly  stated,  there 
are  three  different  types  of  jigs  and  fixtures  used  on  drilling 
machines,  and  mentioned  in  the  order  in  which  they  are  most 
generally  employed,  these  are  as  follows:  (i)  Jigs  or  fixtures  in 
which  the  work  is  held  so  that  one  or  more  holes  may  be  drilled 
in  its  top  face.  (2)  Indexing  jigs  or  fixtures  used  to  provide  for 
the  performance  of  a  sequence  of  operations;  such  fixtures  are 
furnished  with  a  loading  station  at  which  finished  pieces  may 
be  removed  and  new  parts  substituted  while  pieces  held  in  other 
sections  of  the  fixture  are  being  drilled.  (3)  Box  jigs  in  which 
the  work  is  secured;  such  jigs  are  furnished  with  feet  on  two  or 
more  surfaces,  so  that  the  jig  may  be  turned  over  to  provide  for 
drilling  one  or  more  holes  in  two  or  more  surfaces  on  the  work. 

Design  of  Special  Tools  and  Fixtures.  —  Various  special 
forms  of  cutting  tools,  jigs,  and  work-holding  fixtures  are  used 
on  the  drilling  machines  which  are  applied  to  special  work, 
and  in  the  following  some  of  these  tools  will  be  described.  The 
principles  of  tool  design  which  have  been  responsible  for  making 
substantial  increases  in  rates  of  production  will  also  be  con- 
sidered. 

It  will  be  apparent  when  looking  over  the  schedule  of  opera- 
tions presented  in  Chapter  VIII  that  advantage  is  frequently 
taken  of  the  possibility  of  machining  two  or  more  surfaces  on 
the  work  at  a  single  operation.  The  form  of  each  piece  of  work 
to  be  machined  has  been  carefully  studied,  and  after  deciding 
the"  maximum  number  of  surfaces  that  could  be  machined 
simultaneously,  the  tool  designers  have  taken  up  the  problem 
of  working  out  the  form  of  tool  best  adapted  to  meet  the  re- 
quirements of  this  particular  operation.  Another  point  which 
will  attract  the  attention  of  experienced  machine  shop  men 
while  looking  over  the  illustrations  of  typical  parts  machined 
in  the  Bowser  factory  will  be  the  large  number  of  parts  which 


JIGS,  FIXTURES,  AND   SPECIAL  TOOLS  185 

have  several  holes  or  holes  and  surfaces  concentric  with  each 
other.  In  all  cases,  it  is  desirable  to  maintain  this  concentricity 
within  a  reasonable  degree  of  accuracy,  and  there  are  many 
cases  where  a  very  high  degree  of  precision  is  important  to 
obtain  the  desired  alignment  when  these  parts  are  assembled 
together.  Here  advantage  is  taken  of  the  concentric  holes  or 
holes  and  surfaces  on  the  work  to  provide  for  the  use  of  piloted 
tools  which  may  be  depended  upon  to  maintain  the  concentric- 
ity of  different  surfaces  on  the  work  from  some  hole  which  has 
already  been  machined. 

In  many  cases,  it  is  also  necessary  to  hold  vertical  dimen- 
sions on  the  work  within  close  limits.  Various  means  are 
provided  on  the  tools  for  obtaining  this  result.  In  piece  No.  2 
in  the  table  of  operations  (Chapter  VIII),  it  is  required  to 
maintain  the  height  E  from  finished  face  B  to  the  upper  side 
of  the  flange  on  the  rough  casting  within  ^  inch.  The  auto- 
matic tripping  point  for  the  feed  of  the  drilling  machine  spindle 
is  set  as  closely  as  possible,  but,  to  guard  against  lack  of  uni- 
formity in  the  castings,  a  button  A  is  provided  on  the  facing 
tool  which  comes  down  into  contact  with  the  casting  that  is 
being  machined.  This  tool  is  shown  in  Fig.  2.  Normally  the 
power  feed  is  tripped  at  the  same  time  that  this  button  engages 
the  work.  The  drilling  machine  on  which  this  operation  is 
performed  is  set  up  without  having  the  automatic  return  for  the 
drill  spindle  in  operation;  and  after  the  power  feed  has  been 
tripped  the  operator  looks  at  the  button  on  the  tool  to  see  that 
it  is  down  in  contact  with  the  work.  Should  it  happen  that 
this*  engagement  has  not  been  obtained,  he  feeds  the  spindle 
by  hand  before  returning  it  and  setting  up  a  fresh  piece  of  work 
on  the  machine. 

Accuracy  in  Tripping  of  Feed.  —  In  starting  to  describe  the 
special  means  provided  in  the  design  of  tools  to  assure  accuracy 
in  tripping  the  feed  mechanism,  attention  is  called  to  the  fact 
that  Baker  high-duty  drilling  machines  are  especially  adapted 
for  heavy  work,  and  although  the  automatic  trip  for  the  feed 
mechanism  may  be  safely  relied  upon  to  disengage  the  feed 
within  -fa  inch  of  the  desired  point,  it  is  not  safe  to  rely  upon  a 


i86 


MODERN  DRILLING  PRACTICE 


much  closer  limit.  At  the  same  time,  there  are  many  classes  of 
work  where  the  maximum  error  must  not  exceed  0.005  inch, 
and,  in  such  cases,  the  tools  are  designed  to  make  sure  that  the 
work  is  held  to  at  least  this  degree  of  accuracy.  As  shown  in 
Fig.  i,  it  will  be  seen  that  the  arrangement  employed  calls  for 
a  combination  of  work-holding  fixture  and  cutting  tool  which 
work  in  conjunction  with  each  other.  On  the  fixture  there  are 
placed  four  posts  A  that  are  engaged  by  a  flange  B  on  the  cutting 
tool.  This  fixture  and  tool  are  used  for  machining  the  gear 


CUTTING  EDGES 


Machinery 


Fig.  i.     Type  of  Tool  and  Work-holding  Fixture  used  on  Parts 
where  Accuracy  in  Tripping  Feed  is  of  Great  Importance 

shown  in  the  fifth  position  in  the  table  of  operations,  Chapter 
VIII.  It  is  necessary  to  have  the  thickness  of  this  gear  1.750  ± 
0.005  mcn>  and  to  provide  for  obtaining  this  result,  the  tools  are 
so  designed  that  collar  B  comes  into  engagement  with  the  top 
of  posts  A  when  the  cutters  in  the  tool  have  reached  the  desired 
depth  in  the  work. 

To  prevent  binding,  a  ball  thrust  bearing  is  provided  on  the 
tool  above  the  collar.  The  regular  trip  mechanism  on  the 
machine  is  depended  upon  to  disengage  the  feed-worm  clutch 
at  the  desired  point,  but  the  arrangement  of  the  tool  and  work- 
holding  fixture  makes  it  impossible  for  a  slight  lack  of  sensitive- 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS 


I87 


ness  in  the  machine  to  prevent  tripping  to  take  place  until  the 
work  has  been  machined  beyond  the  minimum  dimension  which 
is  called  for.  Those  who  have  not  experimented  with  the 
amount  of  spring  which  is  possible  to  obtain  in  machine  tools 
will  naturally  assume  that  the  use  of  an  arrangement  of  this 
kind  would  result  in  damage  to  the  machine  if  the  trip  for  the 
feed  mechanism  failed  to  operate  at  the  same  time  that  collar  B 
came  into  engagement  with  posts  A.  Experiments  have  shown 
that  it  is  quite  practicable  to  obtain  a  spring  of  from  0.005  to 
o.oio  inch  before  any  damage  is  done,  and,  as  a  result,  the 


Machinery 


Figs.  2,  3,  and  4.  Tool  which  assures  Accuracy  in  Tripping  Feed  — 
Design  of  Under-cutting  Tool  —  Old  and  Improved  Types  of  Fac- 
ing Cutters 

provision  made  in  designing  the  tools  makes  it  impossible  for 
the  bits  to  cut  into  the  work  beyond  the  desired  point.  If  the 
trip  for  the  feed  mechanism  fails  to  function  when  this  point 
has  been  reached,  the  bits  are  prevented  from  cutting  further, 
and  springing  of  the  machine  members  takes  place  until  the 
feed  is  disengaged. 

Design  for  Under-cutting  Tool.  —  Where  it  is  necessary  to 
make  an  under-cut  on  the  work,  use  may  be  profitably  made  of 
the  type  of  tool  shown  in  Fig.  3.  This  tool  is  used  in  making 
the  under-cut  in  the  "  fill  pipe  cap  "  shown  in  the  next  to  last 


1 88  MODERN  DRILLING  PRACTICE 

position  in  the  table  of  operations,  Chapter  VIII.  The  follow- 
ing is  a  brief  explanation  of  the  way  in  which  this  tool  operates : 
Button  A  comes  down  into  engagement  with  the  side  of  the  cast- 
ing in  which  the  under-cut  is  required.  Further  travel  of  the 
feed  mechanism  results  in  compressing  spring  B  which,  in  turn, 
forces  a  cam  C  down  into  contact  with  the  angular  top  of  cutter 
D.  When  cam  C  engages  cutter  D,  further  movement  of  the 
feed  mechanism  of  the  drill  press  results  in  forcing  out  the 
cutting  edge  E  which  is  thus  fed  into  the  work.  This  is  a  simple 
and  convenient  arrangement  for  machining  under-cuts  on  the 
drill  press.  Of  course,  it  is  understood  that,  at  the  same  time 
that  cutting  edge  E  is  being  fed  into  the  work,  the  edge  is  rotat- 
ing to  machine  the  under-cut  all  the  way  around  the  piece. 

Special  Form  of  Facing  Cutters.  —  To  provide  for  the  utiliza- 
tion of  tool  steel  as  far  as  possible,  the  tool  designers  have  worked 
out  a  special  form  for  facing  cutters  used  on  this  battery  of 
drilling  machines.  For  the  purpose  of  comparison,  Fig.  4  shows 
the  old  type  of  facing  cutter  and  the  improved  type  of  cutter 
which  is  now  in  use.  Referring  to  this  illustration,  it  will  be 
seen  that  the  teeth  of  the  old  type  of  cutter  have  all  of  the 
lines  diverging  from  a  common  point  A  at  the  center  of  the  top 
surface  of  the  cutter.  In  sharpening  a  cutter  of  this  type, 
grinding  may  proceed  until  the  teeth  of  the  cutter  are  worn 
down  to  a  point  indicated  by  dotted  lines  B.  When  this  point 
has  been  reached,  the  cutter  is  considered  worn  out. 

It  will  be  apparent  to  anyone  who  gives  this  matter  con- 
sideration that  not  over  approximately  \i\  per  cent  of  the 
steel  in  the  cutter  has  been  used  up  when  the  teeth  are  ground 
down  to  line  B.  To  overcome  this  obvious  waste,  an  improved 
type  of  facing  cutter  was  developed,  in  which  it  will  be  seen 
that  the  flutes  are  milled  to  a  constant  depth.  This  result 
was  easily  accomplished  when  the  tool  designer  once  decided 
to  break  away  from  established  practice  in  grinding  the  teeth 
and  flutes  with  all  lines  converging  from  a  common  point  A}  to 
which  reference  has  already  been  made.  In  sharpening  one 
of  these  improved  cutters,  the  teeth  can  be  ground  right  down 
to  the  bottom  so  that  50  per  cent  of  the  steel  in  the  cutter  is 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS 


189 


used  up;  i.e.,  four  times  as  much  service  is  obtained  as  from 
the  old  type  of  cutter.  A  further  advantage  of  this  improved 
facing  cutter  is  that  the  cutting  edges  of  the  teeth  are  arranged 
tangent  to  a  small  circle  surrounding  the  center  of  the  cutter 
instead  of  having  them  converge  to  this  center.  As  a  result, 
a  shearing  action  is  obtained  which  enables  the  tool  to  cut  more 
freely  than  is  the  case  where  the  cutting  edges  of  the  teeth  are 
radial.  Also,  additional  clearance  for  the  chips  is  provided  by 
having  the  flutes  milled  to  a  constant  depth. 


Machinery 


Fig.  5.     Example  of  Work  done  on  Drilling  Machine 

Special  Features  of  Jigs  and  Fixtures.  —  It  is  not  within  the 
scope  of  this  book  to  enter  into  an  exhaustive  discussion  of  the 
jigs,  fixtures  and  similar  equipment  provided  for  use  in  machin- 
ing the  great  variety  of  parts  that  are  handled  on  Baker  drilling 
machines.  There  are  one  or  two  points,  however,  which  are  of 
more  or  less  general  application,  and  these  will  be  mentioned 
very  briefly.  For  instance,  there  are  many  parts  where  simple 
drilling,  boring,  facing,  and  similar  operations  have  to  be  per- 
formed. Here  it  is  unnecessary  to  provide  a  jig  or  fixture  for 
locating  the  work,  but  means  must  be  provided  for  preventing 


MODERN  DRILLING  PRACTICE 


the  work  from  turning  while  the  machining  operation  is  in 
progress.  For  this  purpose,  considerable  use  is  made  of  what 
are  known  as  slotted  fixtures,  one  of  which  is  shown  on  the 
first  machine  illustrated  in  Fig.  4,  in  Chapter  VIII.  Suppose  a 
square-  or  hexagon-shaped  piece  has  to  be  machined;  one  of 
these  slotted  fixtures  will  be  set  up  on  the  drill  press  table  and 
then  two  rails  will  be  slipped  into  slots  in  the  fixture  at  such  a 
distance  apart  that  the  work  can  just  be  dropped  between 
them.  This  is  only  one  of  the  many  uses  which  is  made  of 
these  slotted  fixtures.  In  the  illustration,  the  fixture  is  shown 
set  up  with  a  work-holding  device  made  out  of  boiler  plate 


Machinery 


Fig.  6.     Fixture  used  to  Hold  Work  while  performing  Disk- 
grinding  Operation  on  Double-spindle  Machine 

that  affords  clearance  for  the  tool  after  it  has  passed  through  the 
work. 

In  most  cases,  the  outstanding  feature  of  the  jig  and  fixture 
equipment  is  the  extreme  simplicity  of  its  design.  This  is 
a  point  of  cardinal  importance  where  high  production  is  aimed 
at,  because  the  least  unnecessary  complication  of  equipment 
would  result  in  a  corresponding  reduction  in  the  speed  of  opera- 
tion and  rate  at  which  parts  could  be  set  up  and  removed  after 
machining.  In  many  cases,  it  has  been  found  feasible  to  use 
standard  three-jaw  chucks  where  circular  parts  have  no  pro- 
jections to  prevent  them  from  turning  around  under  the  spindle. 
Another  feature,  which  is  a  result  of  the  war-time  cost  of  copper 
and  zinc,  is  the  provision  of  special  trays  around  the  fixture 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS 


IQI 


holding  brass  and  bronze  parts  that  are  being  machined.  These 
trays  catch  all  of  the  chips  as  fast  as  they  are  produced  and 
enable  them  to  be  collected  without  loss  —  an  important  saving 
at  the  present  time. 

Tools  and  Fixtures  for  Machining  Cylinder  Bottoms.  —  The 
tools  and  work-holding  fixtures  are  unusually  interesting,  and 
with  the  view  of  giving  a  general  idea  of  this  practice,  a  com- 
plete description  is  given  of  all  cutting  tools,  jigs  and  fixtures 
used  for  machining  the  cylinder  bottom  which  is  shown  first 


-12," 


I3-D 


Machinery 


Fig.  7.    Work-holding  Fixture  used  on  Drilling  Machine 

in   the   tabulated   information  on  machining   operations  (See 
Chapter  VIII,  page  147),  and  also  in  Fig.  5. 

The  first  operation  consists  of  disk-grinding  the  top  and 
bottom  of  this  piece  of  work,  and  a  Besly  double-spindle  ma- 
chine is  used  for  the  purpose.  The  work-holding  fixture  em- 
ployed is  shown  in  Fig.  6,  and  will  be  seen  to  consist  of  a  socket 
in  which  the  work  is  held  in  an  edgewise  position  with  the  top 
and  bottom  extending  out  from  the  fixture  so  that  they  may  be 
eg  aged  by  the  two  disk  wheels.  This  fixture  has  a  handle  A 


IQ2 


MODERN  DRILLING  PRACTICE 


by  which  it  is  pushed  back  and  forth  between  the  disk  wheels 
on  the  machine,  and  these  wheels  are  relied  upon  to  hold  the 
work  in  the  fixture. 

The  second  and  third  operations  consist  of  rough-boring 
and  reaming  hole  A.  In  both  cases  the  work  is  held  in  the 
fixture  shown  in  Fig.  7,  and  the  cutting  tools  are  shown  in 
Figs.  8  and  9.  For  both  boring  and  reaming,  the  speed  is  25 
revolutions  per  minute,  and  the  feed  is  0.018  inch  per  revolu- 
tion. Referring  to  the  tool  shown  in  Fig.  8,  it  will  be  seen  that 


Machinery 


Figs.  8  and  9.     Tools  used  for  Boring  and  Reaming  Hole 
A  in  Work  shown  in  Fig.  5 

the  boring  is  done  by  bits  A,  while  the  function  of  bits  B  is 
merely  to  cut  a  30-degree  chamfer  at  the  top  of  the  hole.  Fine- 
pitch  screws  C  furnish  means  for  making  accurate  adjustment 
of  the  position  of  the  chamfering  cutters.  The  tool  for  ream- 
ing this  hole  requires  no  special  description. 

The  work-holding  fixture,  Figs.  7  and  10,  used  for  these 
two' operations  is  of  simple  design,  three  rails  A  supporting  the 
work  while  a  rail  B  at  each  side  of  the  fixture  prevents  the  work 
from  rotating.  Very  little  time  is  required  to  slide  work  into 
such  a  fixture.  It  will  be  apparent  from  the  dimensions  that 
the  flange  on  the  work  has  considerable  overhang  at  one  end, 
and  as  this  flange  is  at  a  higher  level  than  the  top  of  the  side 
rails  B,  it  would  be  unsupported.  To  overcome  this  difficulty, 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS 


193 


and  at  the  same  time  to  allow  for  slight  variations  in  the  castings, 
a  knurled-headed  screw  C  is  provided  on  the  fixture.  When 
the  operator  sets  a  casting  in  place,  he  adjusts  the  position  of 
this  screw  so  that  it  comes  up  against  the  under  side  of  the 
flange,  thus  supporting  the  work  ready  for  the  machining  opera- 
tion. Particular  attention  is  called  to  the  tongue  D  and  strips 
E  on  the  under  side  of  the  fixture.  This  is  a  standard  con- 
struction on  practically  all  work-holding  fixtures,  the  purpose 
being  to  provide  a  "  floating  "  fixture  which  is  enabled  to  align 
itself  properly  with  the  drill  spindle.  All  fixtures  of  this  type 


Machinery 


Fig.  10.     Perspective  View  of  Boring  and  Reaming  Fixture 
showing  Arrangement  of  Clamping  Mechanism 

rest  on  a  standard  baseplate  (not  shown  in  the  illustration) 
which  is  not  bolted  down  to  the  table  of  the  machine.  The 
upper  side  of  this  plate  has  a  groove  to  receive  tongue  D  and  is 
machined  to  form  bearing  for  strips  E.  On  its  under  side,  this 
plate  has  a  tongue  running  at  right  angles  to  the  groove  in  its 
upper  surface,  and  this  tongue  fits  into  the  T-slot  on  the  drilling 
machine  table.  As  a  result,  the  fixture  floats  in  so  far  as  the 
spindle  of  the  drilling  machine  is  concerned,  although  it  is  held 
in  such  a  way  that  rotation  of  the  fixture  is  impossible. 

The  fourth  operation  consists  of  boring  holes  B  and  C  (Fig.  5) 
and  cutting  a  3o-degree  chamfer  at  the  top  of  hole  B.  For 
this  purpose,  the  same  work-holding  fixture  is  employed  that 
was  used  on  the  two  preceding  operations.  The  cutting  tool 
is  shown  in  Fig.  12,  and  will  be  seen  to  consist  of  cutters  A 
and  B  for  boring  holes  B  and  C  (Fig.  5),  respectively.  The 


194 


MODERN  DRILLING  PRACTICE 


operation  is  performed  at  a  speed  of  100  revolutions  per  minute 
and  a  feed  of  o.oio  inch  per  revolution. 

The  fifth  operation  consists  of  finish-boring  hole  B,  facing 
the  surface  at  the  top  of  the  valve-seat  in  this  hole,  and  cham- 
fering and  facing  the  top  of  hole  C,  for  which  the  fixture  used  is 
shown  in  Fig.  n.  The  fixture  is  practically  the  same  as  that 
used  for  performing  the  preceding  operations,  except  that  the 
portion  of  the  fixture  under  the  part  of  the  work  that  is  being 
machined  is  furnished  with  solid  metal  surfaces  shown  at  A, 
instead  of  simply  having  the  work  supported  by  a  narrow  rail. 


12- 


Machinery 


Fig.  ii.     Work-holding  Fixture  in  which  Casting  is  held  for 
Finish-boring  Holes  B  and  C,  Fig.  5 

The  reason  for  this  construction  is  that,  while  the  previous  type 
of  fixture  is  satisfactory  for  the  performance  of  roughing  opera- 
tions, for  taking  the  finishing  cut  it  is  possible  for  the  work  to  be 
cocked  sufficiently  out  of  alignment  to  produce  an  appreciable 
error.  It  is  to  guard  against  the  possibility  of  such  a  contin- 
gency that  the  present  type  of  fixture  is  employed.  This  fix- 
ture is  used  for  the  performance  of  several  other  operations, 
and  the  openings  at  B  and  C  with  solid  metal  surfaces  sur- 
rounding them  have  no  special  significance  in  connection  with 
the  present  operation.  The  cutter  used  for  taking  this  finish- 
ing cut  is  shown  in  Fig.  13.  It  will  be  seen  that  cutter  A  reams 
hole  B,  while  cutter  B  faces  the  top  of  this  hole.  Chamfering 


JIGS,   FIXTURES,  AND   SPECIAL  TOOLS 


195 


and  counterboring  the  top  of  hole  C  is  done  by  cutter  C,  while 
facing  the  top  of  this  hole  is  done  by  cutter  D.  Cutters  C  and 
D  are  piloted  in  hole  C  to  assure  accurate  alignment.  This 
operation  is  performed  at  a  speed  of  100  revolutions  per  minute 
and  a  feed  of  0.014  inch  per  revolution. 

The  sixth  operation  consists  of  tapping  hole  C,  for  which 
purpose  a  No.  9  tap,  made  by  the  Manufacturers'  Equipment 
Co.,  of  Chicago,  is  employed,  this  tap  being  furnished  with  a 
special  pilot  shown  in  Fig.  14,  which  runs  in  hole  B.  This 


Figs.  12  to  15.  Tools  for  Rough-  and  Finish-boring  Holes  B  and 
C  (Fig.  5),  Special  Tap  Pilot  for  Hole  C,  and  Valve-seating 
Tool  for  Top  of  Hole  B 

pilot  is  shown  at  A  in  Fig.  14,  and  is  held  in  place  in  the  tap 
by  a  draw-bolt  B.  Above  the  collar  on  this  draw-bolt  the  de- 
sign is  similar  to  the  regular  bolt  used  on  the  standard  tap, 
but  the  thin  extension  B  below  the  collar  is  provided  to  reach 
down  and  hold  pilot  A  in  place.  The  fixture  used  for  perform- 
ing this  operation  is  the  same  as  that  used  on  the  second,  third, 
and  fourth  operations.  The  work  is  done  at  a  speed  of  25 
revolutions  per  minute. 

The  seventh  operation  consists  of  finishing  the  valve-seat. 
The  work  is  set  on  the  bed  of  the  machine  without  using  a 


i96 


MODERN  DRILLING  PRACTICE 


fixture,  and  the  tool  used  is  shown  in  Fig.  15.  The  valve-seat 
cutter  is  shown  at  A  and  collar  B  is  provided  on  the  tool  which 
enables  the  seating  tool  to  cut  in  to  exactly  the  proper  depth. 
This  operation  is  performed  at  a  speed  of  100  revolutions  per 
minute  with  hand  feed. 

After  the  valve  has  been  seated,  the  eighth  operation  is  to 
turn  the  outside  of  union  D,  face  the  top  of  this  union,  and 
counterbore  for  the  brass  insert  E.  The  work-holding  fixture 
used  for  this  purpose  is  shown  in  Fig.  16;  and  it  will  be  seen 
to  be  practically  identical  with  the  fixture  used  for  performing 
the  second,  third,  and  fourth  operations.  It  consists  of-  three 


Machinery 


Fig.  1 6.     Fixture  used  for  Holding  Work  while  Turning 
and  Facing  Union  D,  Fig.  5 

rails  A  to  support  the  work  and  two  side  rails  B  to  prevent 
the  work  from  rotating.  The  cutting  tool  used  for  this  purpose 
is  shown  in  Fig.  17,  from  which  it  will  be  seen  that  three  bits  A 
provide  for  turning  the  outside  of  the  union,  three  cutters  B 
for  counterboring  for  the  brass  insert  E,  and  tool  C  for  facing 
the  top  of  the  union.  The  design  of  this  tool  is  worked  out  in 
such  a  way  that  two  lock-nuts  D  support  the  bits  A  and  B  from 
the  top  and  provide  accurate  means  of  adjusting  them  in  the 
desired  vertical  position. 

At  the  same  time,  the  bits  are  furnished  radial  support  by 
means  of  set-screws  E  carried  in  a  collar  surrounding  the  lower 
part  of  the  tool.  This  is  a  somewhat  old  tool,  and  recently 


JIGS,  FIXTURES,  AND   SPECIAL  TOOLS 


197 


the  design  of  this  type  of  tool  has  been  considerably  modified 
to  provide  better  radial  support  for  the  cutters.  In  designing 
tools  of  this  type,  it  is  now  the  practice  to  bring  the  collar  down 
within  about  J  inch  of  the  cutting  edge  of  the  bits,  instead  of 
having  the  bits  overhang  approximately  ij  inch.  In  this  way 
there  is  far  better  support  and  the  possibility  of  their  springing 
away  from  the  work  is  very  materially  reduced.  Some  tool 
designers  will  be  inclined  to  say  that  the  amount  of  spring 
which  could  possibly  occur  in  a  tool  of  the  type  shown  in  Fig.  1 7 
is  so  small  that  the  change  in  design  is  scarcely  worth  while. 


Figs.  17,  1 8,  and  19.  Tool  for  Turning,  Facing,  and  Boring  Union 
D,  Tool  for  Reaming  Seat  for  Bushing  E,  and  Tool  for  Cham- 
fering Bushing  E 

Granting  that  this  is  the  case,  the  Bowser  tool  designers  did 
not  feel  satisfied  with  any  form  of  construction  that  left  the 
possibility  for  an  error  which  there  was  any  way  to  overcome. 
The  speed  at  which  this  operation  is  conducted  is  72  revolutions 
per  minute  with  a  feed  of  0.012  inch  per  revolution. 

The  ninth  operation  consists  of  reaming  the  bore  for  the 
brass  insert  E.  The  same  fixture  is  used  as  for  the  preceding 
operation,  and  the  tool  employed  is  shown  in  Fig.  18,  which 
consists  of  a  simple  reaming  cutter  A  mounted  on  a  suitable 
shank.  The  operation  is  performed  at  a  speed  of  100  revolu- 
tions per  minute,  with  hand  feed. 


MODERN  DRILLING  PRACTICE 


After  reaming  the  hole  for  the  brass  insert,  the  tenth  opera- 
tion is  to  thread  the  outside  of  union  D,  which  is  done  with  a 
threading  die.  The  same  fixture  is  used  as  for  the  two  pre- 
ceding operations,  and  the  work  is  done  at  a  speed  of  25  revolu- 
tions per  minute.  After  threading,  the  work  is  ready  for  the 
eleventh  operation,  which  consists  of  pressing  the  brass  insert 
into  place.  This  is  done  with  a  portable  arbor  press,  which  is 

brought  up  to  the  gang 
drills  at  such  times  as  it  is 
required  for  service.  The 
arbor  press  is  mounted 
on  a  skid,  so  that  it  can 
be  carried  on  an  elevat- 
ing truck;  it  is  motor- 
driven  and  connected  to 
the  power  circuit  arranged 
on  this  battery  of  drilling 
machines. 

The  twelfth  operation 
consists  of  cutting  the 
valve-seat  in  brass  insert 


%  DRILL  ROD  HARDEN 
PRESS  FIT 


Machinery 


Fig.  20.    Jig  used  for  Drilling  Holes  F,  Fig.  5 

E  in  the  union.  The  work  is  held  in  the  same  fixture  as  for  the 
preceding  operation,  and  the  tool  used  is  shown  in  Fig.  19.  It 
will  be  seen  that  this  is  a  simple  angular  mill  A  mounted  on  a 
suitable  shank.  A  guard  B  is  placed  around  the  cutter  to 
provide  for  the  operator's  safety.  The  operation  is  performed 
at  a  speed  of  180  revolutions  per  minute,  and  a  feed  of  o.oio 
inch  per  revolution. 

The  thirteenth  operation  consists  of  drilling  two  holes  F. 
The  same  work-holding  fixture  is  used  as  in  the  preceding  opera- 
tion, and  the  holes  are  located  by  means  of  a  jig  shown  in  Fig.  20. 
Pin  A  is  dropped  into  the  cored  hole  G  on  the  work  and  locating 
pins  B  enter  the  rectangular  shaped  hole  in  the  work,  shown  by 
dotted  lines  between  the  holes  F  which  are  to  be  drilled.  When 
handwheel  C  is  turned  so  that  tapered  block  D  is  drawn  up 
between  the  heads  of  pins  B,  these  pins  are  forced  outward, 
which  results  in  clamping  the  jig  firmly  in  place  over  the  work. 


JIGS,  FIXTURES,  AND  SPECIAL  TOOLS  199 

Hardened  steel  bushings,  through  which  the  holes  are  drilled, 
are  located  in  holes  E  in  the  jig.  The  drilling  operation  is 
performed  at  a  speed  of  280  revolutions  per  minute  with  a  feed 
of  o.oio  inch  per  revolution.  After  these  holes  have  been 
drilled,  the  jig  is  removed  from  the  work,  which  is  left  in  posi- 
tion in  the  fixture  ready  for  the  performance  of  the  fourteenth 
operation.  This  consists  of  tapping  the  holes  F.  This  tapping 
operation  is  performed  at  a  speed  of  72  revolutions  per  minute. 

Of  these  fourteen  operations,  it  will  be  recalled  that  Opera- 
tion i  is  done  on  a  disk  grinder,  while  Operation  n  consists 
of  pressing  a  brass  bushing  into  place  in  the  work,  a  portable 
arbor  press  being  used  for  this  purpose.  As  a  result,  there 
are  twelve  operations  that  are  performed  on  the  Baker  drilling 
machines,  and  these  are  divided  up  into  three  groups  of  four 
operations  each.  In  order  to  have  the  relative  amount  of 
time  taken  by  different  operations  work  out  to  the  best  pos- 
sible advantage,  the  following  grouping  was  decided  upon: 
Operations  2,  3,  13,  and  14  are  performed  on  a  group  of  four 
machines;  Operations  4,  5,  6,  and  7  are  next  performed  on  this 
group  of  four  machines  at  the  second  setting;  and  Operations 
8,  9,  10,  and  12  are  performed  at  the  third  setting  of  these  four 
machines. 

It  will  be  recalled  that  in  Chapter  VIII  attention  was  directed 
to  the  fact  that  an  endeavor  is  always  made  to  select  groups 
of  four  operations  in  such  a  way  that  all  four  machines  of  the 
group  may  be  kept  as  constantly  employed  as  possible.  The 
grouping  together  of  Operations  2,  3, 13,  and  14  is  a  good  example 
of  this  kind.  Operation  13  calls  for  drilling  two  holes  F,  one 
at  a  time,  and  Operation  14  consists  of  tapping  these  holes 
one  at  a  time.  To  provide  for  performing  these  two  double 
operations  without  keeping  other  machines  idle,  they  are  grouped 
with  Operations  2  and  3,  which  consist  of  boring  and  reaming 
the  large  hole  A ,  and  take  as  much  time  as  the  double  operations 
of  drilling  and  tapping  two  holes  F,  one  at  a  time.  In  handling 
a  battery  of  four  machines,  the  operator  goes  from  Operation  2 
to  Operation  3,  then  to  Operation  13,  where  he  starts  drilling 
one  hole,  then  to  Operation  14,  where  he  starts  tapping  one 


13  G 


200  MODERN  DRILLING  PRACTICE 

hole  and  waits  until  this  operation  is  completed,  the  time  being 
only  a  few  seconds.  He  then  starts  the  tap  in  the  second  hole 
for  Operation  14,  after  which  he  starts  the  drill  for  the  second 
hole  in  Operation  13.  After  this,  he  goes  back  to  Operation  2 
to  start  work  on  a  fresh  piece,  and  this  order  of  procedure  is 
followed  continuously,  with  the  result  that  all  machines  are 
kept  constantly  employed.  In  conclusion,  it  may  be  mentioned 
that  only  one  group  of  four  machines  is  working  on  the  same 
piece  at  a  time.  After  the  first  four  operations  have  been  per- 
formed on  all  pieces,  this  same  group  of  four  machines  starts  on 
the  next  four  operations;  and  when  these  have  been  completed, 
the  final  group  of  four  operations  is  performed  on  this  set  of 
machines.  It  would  not  do  to  have  twelve  machines  out  of  a 
battery  of  twenty-eight  working  on  one  part. 

Concerning  Rates  of  Production.  —  As  most  of  the  work 
handled  on  this  battery  of  high-duty  drilling  machines  is  of  a 
character  where  an  extremely  high  degree  of  accuracy  is  not 
required,  the  rates  of  production  obtained  in  performing  ma- 
chining operations  become  a  matter  of  unusual  importance. 
A  good  idea  of  the  actual  output  in  machining  various  parts 
which  could  be  handled  with  a  sl^op  equipment  of  this  character 
will  be  gathered  from  a  study  of  the  machining  operations  and 
rates  of  production  which  are  tabulated  in  a  preceding  chapter. 
It  will  at  once  be  apparent  to  the  experienced  production  engi- 
neer that  these  rates  of  output  are  very  satisfactory,  but  a  man 
who  is  considering  the  problem  of  selecting  equipment  for  ma- 
chining a  given  line  of  work  which  might  be  handled  on  drilling 
machines  will  naturally  ask  himself  the  question,  "  Is  there 
no  better  way  in  which  I  could  machine  these  parts?  "  An 
answer  to  this  question  is  found  in  the  experience  of  S.  F.  Bowser 
&  Co.  during  the  past  two  years.  This  firm's  shops  have  been 
so  rushed  with  work  that  a  practice  has  been  made  of  arrang- 
ing with  outside  concerns  to  machine  work  on  a  contract  basis. 
In  many  cases  the  figures  submitted  for  machining  parts  which 
are  ordinarily  handled  in  the  drilling  machine  department  have 
been  so  far  above  the  company's  own  production  costs  that  a 
good  deal  of  hesitation  was  felt  about  letting  contracts  to  these 


JIGS,  FIXTURES,  AND   SPECIAL  TOOLS  2OI 

bidders.  Investigations  which  were  conducted,  however,  went 
to  show  that  the  margin  of  profit  made  on  the  work  by  these 
outside  concerns  was  not  at  all  excessive,  and  as  most  of  the 
bids  obtained  from  outside  machine  shops  were  considerably 
above  the  cost  of  producing  work  on  drilling  machines  —  after 
deducting  a  reasonable  margin  of  profit  —  it  is  fair  to  conclude 
that  these  shops  based  their  bids  upon  the  use  of  equipment 
which  was  unable  to  compete  with  the  highly  specialized  tools 
and  methods  which  have  been  described. 


CHAPTER  X 
DEEP-HOLE  DRILLING 

A  DEEP  hole  is  usually  defined  as  a  hole  the  depth  of  which 
is  equal  to  at  least  five  times  the  diameter,  although  some 
authorities  define  it  as  one  in  which  the  depth  is  equal  to  four 
diameters.  In  deep-hole  drilling,  special  precautions  must  be 
taken  for  two  reasons:  In  the  first  place,  trouble  is  likely  to 
be  experienced  through  breaking  of  the  drill  as  a  result  of  chips 
clogging  the  drill  in  the  hole;  and,  secondly,  further  trouble 
may  result  through  failure  to  obtain  the  desired  cooling  and 
lubricating  action  on  account  of  having  the  chips  prevent  lu- 
bricant from  reaching  the  cutting  point  of  the  drill.  Numerous 
expedients  are  employed,  to  prevent  trouble  from  chips  clogging 
the  drill  in  the  hole.  In  drilling  fairly  deep  holes  with  ordinary 
drilling  equipment,  it  is  quite  general  practice  to  back  the  drill 
out  of  the  hole  at  frequent  intervals  in  order  that  the  chips  may 
be  cleared  from  the  drill.  This  also  guards  against  an  accumu- 
lation of  chips  preventing  lubricant  from  reaching  the  cutting 
point.  A  better  way  to  assure  efficient  lubrication  of  drills 
used  in  deep  holes  is  to  use  oil-tube  tools  which  are  furnished 
with  ducts  that  carry  the  oil  or  cutting  compound  direct  to  the 
point  of  the  drill  where  its  action  is  required.  Recently  it  has 
become  quite  general  practice  to  adopt  the  use  of  inverted  drills 
for  deep-hole  work,  because  it  has  been  found  that  where  an  in- 
verted drill  operates  from  below  the  work,  it  is  a  much  easier 
matter  for  the  chips  to  clear  themselves  from  the  hole.  Where 
this  inverted  drilling  is  employed,  it  is  not  often  necessary 
to  resort  to  the  practice  of  backing  the  drill  out  of  the  hole  at 
frequent  intervals,  in  the  manner  which  has  just  been  men- 
tioned. 

When  holes  are  very  deep  or  long  in  proportion  to  their  diam- 
eter, special  drills  and  machines  are  required.  The  drilling  of 


DEEP-HOLE  DRILLING 


203 


holes  in  rifle  barrels  is  an  example  of  the  class  of  deep-hole 
work  necessitating  the  use  of  special  equipment.  Some  of  the 
tools  and  methods  employed  for  deep-hole  drilling  in  connection 
with  general  manufacturing  will  first  be  described,  and  then  the 
more  special  equipment  required  for  rifle  barrel  drilling  will  be 
considered. 


Fig.  i. 


Gang  Drilling  Machine  arranged  for  Drilling  by 
Inverted  Method 


Inverted  Drilling  for  Deep-hole  Work.  —  The  inverted 
method  of  drilling  consists  in  holding  the  drill  stationary  in  an 
inverted  position  and  revolving  the  part  to  be  drilled.  Fig.  i 
shows  a  four-spindle  gang  drilling  machine  built  by  the  Rock- 
ford  Drilling  Machine  Co.,  which  is  equipped  with  two-jaw 
chucks  mounted  on  the  spindles  so  that  work  may  be  rotated 
by  the  spindles  and  fed  down  onto  inverted  drills  which  are 
held  stationary  on  the  table  of  the  machine.  The  principle 


204 


MODERN  DRILLING  PRACTICE 


will  be  clearly  understood  by  reference  to  the  illustration.  The 
advantage  of  this  method  of  drilling  is  that  the  chips  are  cleared 
more  easily  from  the  deep  holes  than  would  be  the  case  with  the 
usual  relation  of  the  work  and  drill.  The  work  consists  of  yoke 
forgings  for  universal  joints,  and  these  pieces  are  fed  down 
over  the  drills  so  that,  after  the  drilling  operation  has  been 
completed,  the  end  of  the  forging  is  faced  by  the  stationary 


GEOMETRIC  SELF- 
CUP  TURNING  TOOL         OPENING  DIE-HEAD 


FLOATING  HOLDER 


Machinery 


Fig.  2.    Fixture  for  Drilling,  Turning,  and  Threading  Work 

tool  A,  which  will  be  seen  in  the  holder  at  the  base  of  each 
drill.  The  work  to  be  drilled  is  a  drop-forging  containing  from 
0.15  to  0.25  per  cent  of  carbon,  from  0.30  to  0.60  per  cent  of 
manganese,  phosphorus  below  0.045  Per  cent>  and  sulphur  be- 
low 0.05  per  cent.  The  holes  to  be  drilled  are  \  inch  in  diameter 
by  if  inch  deep  and  approximately  1000  pieces  are  drilled  on 
this  four-spindle  machine  in  a  ten-hour  working  day.  Fig.  2 
shows  a  detailed  view  of  the  fixture  provided  for  handling  a 


DEEP-HOLE  DRILLING 


205 


Fig.  3.     Drilling  Machine  machining  i8-pound  High-explosive  Shells 

somewhat  similar  job,  although  in  this  case,  after  being  drilled, 
the  work  is  turned  on  the  outside  and  then  threaded.  As  in 
the  previous  case,  the  drill  is  held  stationary  on  the  machine 
table  and  a  chuck  carried  on  the  drilling  machine  spindle  pro- 
vides for  rotating  the  work  and  feeding  it  down  onto  the  drill. 


206  MODERN  DRILLING  PRACTICE 

After  the  drilling  operation  has  been  completed,  the  fixture 
is  indexed  to  bring  the  cup  turning  tool,  or  hollow-mill,  into 
the  operating  position  to  provide  for  turning  the  outside  of  the 
work;  and  after  this  operation  has  been  completed,  the  fixture 
is  again  indexed  to  bring  the  geometric  self-opening  threading 
die  into  position  for  threading. 


Fig.  4.    Close  View  of  Tool  Equipment  of  Machine  shown  in  Fig.  3 

Inverted  Tools  held  on  Indexing  Fixture.  —  Fig.  3  shows  a 
drilling  machine  built  by  the  Barnes  Drill  Co.  for  machining 
1 8-pound  high-explosive  shells,  and  Fig.  4  shows  a  close  view 
of  the  tool  equipment  on  this  machine.  The  selection  of  this 
type  of  equipment  was  decided  upon  at  the  factory  where  the 
machines  are  used,  due  to  inability  to  secure  reasonable  de- 
liveries on  the  types  of  machine  tools  that  would  ordinarily  be 
selected  for  the  performance  of  machining  operations  of  this 
kind.  A  battery  of  eight  of  these  self-oiling  22-inch  machines 


DEEP-HOLE  DRILLING  207 

was  installed,  and  the  results  obtained  have  been  entirely  satis- 
factory. The  shell  to  be  machined  is  held  in  a  fixture  A  secured 
to  the  drilling  machine  spindle,  while  the  tools  required  for  the 
performance  of  successive  operations  are  carried  on  an  indexing 
fixture  mounted  on  the  machine  table.  With  this  arrange- 
ment the  work  is  revolved  and  fed  down  onto  a  stationary 
inverted  tool,  so  that  advantage  may  be  taken  of  the  greater 
ease  with  which  chips  clear  themselves  from  an  inverted  hole 
of  this  kind.  After  each  operation  has  been  completed,  the 
tool-holding  fixture  is  indexed  to  bring  the  next  tool  into  the 
operating  position.  The  first  operation  is  to  spot-drill  and 
rough-form  the  nose  of  the  shell  with  tools  held  in  holder  C. 
A  guiding  ring  is  provided  for  the  work  so  that  it  cannot  spring 
away  from  the  cut.  The  operation  is  performed  at  92  revolu- 
tions per  minute,  with  a  feed  of  0.013  inch  per  revolution.  The 
spotting  is  done  with  a  short  twist  drill,  and  rough-forming  of 
the  nose  with  three  turning  tools,  which  are  stepped  so  that 
they  cut  to  different  depths,  leaving  an  irregular  surface. 

The  second  operation  is  to  drill  the  hole  in  the  shell  to  the 
required  depth;  for  this  purpose,  drill  D  is  used,  which  is  i^f 
inch  in  diameter.  The  drilling  operation  is  performed  at  145 
revolutions  per  minute  with  a  feed  of  0.013  incn  Per  revolution. 
The  third  operation  is  to  rough-ream  the  hole  with  reamer  E, 
which  is  formed  at  the  end  to  finish  the  bottom  of  the  shell 
cavity  to  the  required  shape.  The  operation  is  performed  at 
37  revolutions  per  minute  with  a  feed  of  0.093  incn  per  revolu- 
tion. The  fourth  operation  is  to  finish-form  the  nose  with  a 
form  cutter  located  in  holder  F,  which  is  bronze  lined.  The 
spindle  runs  at  45  revolutions  per  minute,  and  is  fed  down  by 
hand.  The  fifth  operation  is  to  cut  the  step  and  bevel  on  the 
nose  of  the  shell.  For  this  operation,  the  tool  is  supported 
by  a  bronze-lined  tool-holder  G  and  the  machine  is  operated 
at  the  same  speed  and  feed  as  for  the  fourth  operation.  The 
sixth  and  final  operation  is  to  finish-ream  the  hole  in  the  shell 
with  reamer  H.  Great  care  is  required  in  the  performance  of 
this  operation,  as  specifications  for  the  shells  require  that,  when 
a  light  is  dropped  into  the  hole,  the  surface  will  show  a  uniform 


208 


MODERN  DRILLING  PRACTICE 


polish  in  all  places.  The  finish-reaming  operation  is  performed 
with  the  spindle  rotating  at  37  revolutions  per  minute  with  a 
down  feed  of  0.093  mcn  Per  revolution. 

Vertical  Deep-hole  Drill- 
ing Machine.  —  The  deep- 
hole  drilling  machine  shown 
in  Fig.  5  was  built  original- 
ly by  the  Charles  Stecher 
Co.  for  drilling  holes  in  the 
solid  forgings  from  which 
machine  tool  spindles  are 
made,  and  the  first  machine 
was  used  for  drilling  the 
spindles  of  the  Stecher 
screw  machines.  Several 
machines  of  this  design  were 
subsequently  sold  to  other 
machine  tool  builders  for 
the  same  service.  Recent- 
ly this  machine  has  been 
enlarged  and  its  design  has 
been  altered  to  adapt  it 
for  drilling  recoil  cylinders, 
axles  for  gun  carriages,  and 
gun  barrels  and  jackets  for 
the  smaller  guns.  The  larg- 
est machines  built  to  date 
have  a  bore  through  the 
spindle  8  inches  in  diam- 
eter and  a  feed  of  96  inches. 
These  dimensions  can  easily 

be    increased.     This    ma- 
Fig.  5.     Vertical  Deep-hole  Drilling  Machine  .  ,   r  ,. 

chine  is  used  for  roughing 

out  the  first  hole  from  the  solid  forging  and  on  finishing  operations 
where  wood-packed  reamers  are  used.  For  roughing  out  holes 
from  the  solid,  an  ordinary  drill  point  is  used,  inserted  in  a  bar 
slightly  smaller  in  diameter  than  the  bore,  and  the  bar  is  fluted 


DEEP-HOLE  DRILLING  209 

for  chip  clearance.  The  vertical  feature  allows  the  chips  to  clear 
freely  without  the  use  of  high  pressure  on  the  cutting  compound, 
and  it  is  not  necessary  to  give  special  consideration  to  this 
problem,  which  is  the  chief  source  of  trouble  in  drilling  deep 
holes  in  a  horizontal  position.  Drilling  artillery  axles  in  these 
machines  with  a  drill  point  3.185  inches  in  diameter,  using 
0.012  inch  feed  and  driving  the  spindle  at  48  revolutions  per 
minute,  the  work  is  drilled  to  a  depth  of  57  inches  without 
trouble  from  chips  clogging,  and,  as  the  work  revolves,  the 
hole  is  straight  and  concentric  to  the  bottom. 

The  spindle  is  equipped  with  an  air  chuck  at  each  end,  con- 
trolled by  an  operating  valve  which  is  conveniently  reached 
from  the  floor.  The  work  can  be  lowered  through  the  spindle 
with  an  overhead  tackle,  but  where  head-room  is  limited  the 
work  can  be  placed  on  a  carriage  and  raised  through  the  spin- 
dle from  below.  An  operator  and  helper  can  operate  a  number 
of  these  machines,  depending  upon  the  nature  of  the  work 
accomplished.  Where  wood-packed  reamers  are  used,  the 
reamer  is  drawn  down  through  the  work  by  a  draw-rod  and  is 
guided  and  held  against  turning  by  a  rigid  bushing  above  the 
spindle;  or  the  work  can  be  changed  from  the  rougher  to  a 
special  machine  designed  for  reaming,  which  is  constructed  with 
the  hollow  spindle,  in  which  the  work  is  rotated,  at  the  base  end 
of  the  column  and  the  drill  carriage  above,  feeding  the  reamer 
down  through  the  work  and  washing  the  chips  ahead.  By 
revolving  the  work,  the  best  results  are  obtained,  and  the  ver- 
tical lay-out  permits  the  use  of  simple  tooling,  with  consequent 
low  tooling  cost.  The  design  of  these  machines  permits  of 
grouping  the  equipment,  which  is  the  ideal  arrangement  for 
handling  four  or  five  machines  by  one  operator  and  helper 
without  decreasing  their  production. 

Horizontal  Deep-hole  Drilling  Machine.  —  The  machine 
shown  in  Fig.  6  was  designed  for  the  special  purpose  of  drilling 
the  long  small  hole  through  the  length  of  the  steel  block  shown 
in  Fig.  7,  which  is  a  part  of  a  machine  gun.  The  making  of 
this  part  is  started  in  the  block  form  and  the  hole  is  put  in  first, 
as  it  is  the  most  difficult  to  locate  accurately.  All  the  subse- 


210 


MODERN  DRILLING  PRACTICE 


quent  machining  is  gaged  from  the  finished  hole.  The  drilling 
of  this  hole  is  difficult,  on  account  of  its  small  diameter  as  com- 
pared with  its  length.  The  test  for  straightness  of  hole  was  the 
free  fit  of  a  hard  ground  arbor  sized  to  0.0005  mcn  ^ess  than  the 
low  diameter  limits  given  in  Fig.  7.  To  pass  inspection,  the  pin 
had  to  drop  through  the  full  length  of  the  hole  by  its  own  weight. 


Fig.  6.     Horizontal  Deep-hole  Drilling  Machine 

The  limits  for  this  hole  diameter  are  0.002  and  0.003  mcn> 
and  for  depth,  ±0.007  inch.  The  leading  feature  of  this  ma- 
chine is  that  both  the  work  and  tools  revolve,  the  proper  speed 
for  each  being  determined  from  experimental  tests.  A  set 
of  seven  tools  is  used  to  produce  the  hole.  The  large  portion 
of  the  hole  requires  a  spotting  tool,  a  twist  drill,  and  a  reamer, 
the  reamer  having  a,  spotting  tool  on  its  end  to  start  the  middle 


DEEP-HOLE  DRILLING 


211 


hole.  The  middle  hole  requires  a  drill  and  reamer,  the  reamer 
also  having  a  spotting  tool  on  its  end  to  start  the  small  hole. 
The  small  hole  is  drilled  and  reamed.  Each  individual  tool  is 
fitted  with  a  knurled  taper  socket  lock  shank  that  permits  the 
tools  to  be  quickly  interchanged  and  locked  firmly  in  place  on 
the  tailstock  spindle. 

The  tailstock  has  two  drilling  positions,  the  outward  position 
being  used  for  the  three  operations  on  the  large  hole  and  the 
inner  position  for  the  operations  on  the  middle  and  small  holes. 
The  tailstock  is  moved  by  a  toggle  lever  motion  that  is  self- 
locking  in  both  positions.  The  tailstock  spindle  runs  on  ball 


-4.8543  ±JJ:g° 


H 2.098518:88? *< 2.1653+S  — 


Machinery 


Fig.  7.     Gun  Part  drilled  in  Machine  shown  in  Fig.  6 

bearings  mounted  in  a  feed  sleeve  that  is  actuated  through  a 
rack  and  pinion.  The  headstock  has  the  work  placed  inside 
and  the  cover  closed  so  as  to  lock  it  in  place  while  revolving. 
To  avoid  any  possible  flying  out  of  the  block  in  case  the  cover 
should  accidentally  open,  a  guard  is  provided  that  surrounds 
the  spindle  on  all  sides.  In  Fig.  6  the  guard  is  shown  open, 
but  when  closed  it  is  locked  by  a  snap-catch.  After  a  block  has 
been  completely  drilled,  it  is  necessary  to  bring  the  headstock 
spindle  to  a  dead  stop  so  as  to  permit  the  operator  to  open  the 
swing  cover,  remove  the  block  and  put  in  a  blank  block.  Rota- 
tion of  the  headstock  and  tailstock  spindles  is  stopped  by  throw- 
ing the  friction  drive  plates  on  the  countershaft  out  of  contact. 
This  is  done  by  the  operator  by  means  of  a  foot-pedal  and  long 


212  MODERN  DRILLING  PRACTICE 

link  connection.  To  bring  the  heads tock  spindle  to  a  quick 
stop,  toggle-joint  shoe  brakes  that  act  on  a  pulley  on  the  jack- 
shaft  are  automatically  put  into  action  when  the  guard  is  opened 
and  released  when  it  is  shut.  To  the  front  end  of  the  inner 
bearing  of  the  headstock,  there  is  screwed  a  stationary  cover 
which  supports  the  guide  bushings  required  for  the  tools,  and 
which  also  acts  on  a  reservoir  for  forcing  the  cutting  oil  to  the 
tools. 

Why  Work  is  revolved  when  Drilling  Holes  of  Unusual 
Depth.  —  The  principle  involved  in  common  drill  presses  where 
the  drill  is  given  a  rotary  motion  simultaneously  with  the  for- 
ward motion  for  feeding  is  the  one  least  adapted  to  produce  a 
straight  and  true  hole,  and  this  method  cannot  be  employed  for 
drilling  very  deep  holes  such,  for  example,  as  the  holes  in  rifle 
barrels.  Better  results  are  obtained  by  giving  only  a  rotary 
motion  to  the  drill,  and  feeding  the  work  toward  it.  It  has 
been  found,  however,  that,  for  drilling  deep  holes,  the  reversal 
of  this,  that  is,  imparting  a  rotary  motion  to  the  work,  and  the 
feed  motion  to  the  drill  will  answer  the  purpose  still  better. 
While  a  material  difference  between  the  latter  two  methods 
might  not  be  apparent,  an  analysis  of  the  conditions  involved 
will  show  that  there  is  a  decided  difference  in  the  action  of  the 
drill.  If  the  drill  rotates  and  the  work  is  fed  forward,  the  drill, 
when  deviating  from  its  true  course,  will  be  caused  to  increase 
its  deviation  still  more,  by  the  wedge  action  of  the  part  B  (Fig.  8) 
which  tends  to  move  in  the  direction  BA  when  the  work  is  fed 
forward.  In  the  case  of  the  work  rotating  and  the  drill  being 
fed  forward,  as  shown  to  the  right,  the  point  of  the  drill  when 
not  running  true  will  be  carried  around  by  the  work  in  a  circle 
with  the  radius  a,  thus  tending  to  bend  the  drill  in  various 
directions.  The  drill  is  by  this  action  forced  back  into  the 
course  of  "  least  resistance,"  as  it  is  evident  that  the  bending 
action,  being  exerted  on  the  drill  in  all  directions,  will  tend  to 
carry  the  point  back  to  the  axis  of  the  work  where  no  bending 
action  will  appear. 

The  difficulties  to  be  overcome  in  producing  deep  drilled 
holes  can  be  classified  in  three  groups.  In  the  first  place,  the 


DEEP-HOLE  DRILLING 


213 


drill,  if  applied  in  the  ordinary  manner,  has  a  great  tendency 
to  run  out,  thus  producing  a  hole  that  is  neither  straight  nor 
uniform  in  diameter;  in  the  second  place,  great  difficulties  are 
encountered  in  trying  to  remove  the  chips  in  a  satisfactory 
manner;  and,  in  the  third  place,  the  heating  of  the  cutting  tool 


Sfaefflnery 


Fig.  8. 


Comparison  between  Action  of  Cutting  Tool  when  Drill 
and  when  Work  revolves 


is  difficult  to  prevent.  The  first  difficulty  is  overcome  by 
adopting  the  method  previously  referred  to,  and  the  chips 
are  carried  off  by  forcing  a  fluid  into  the  hole,  which  upon  its 
return  carries  with  it  the  chips.  This  fluid  being  oil  will  serve 
the  double  purpose  of  carrying  away  the  chips  and  lubricating 
the  cutting  tool,  keeping  it  at  a  normal  temperature. 

Drill  for  Deep  Holes.  —  A  highly  satisfactory  drill  for  use  in 
drilling  deep  holes  is  one  brought  out  by  the  Pratt  &  Whitney 


214 


MODERN  DRILLING  PRACTICE 


Co.,  principally  for  use  in  connection  with  their  gun-barrel 
drilling  machines.  The  tool  in  question  is  a  development  of 
the  old  D  or  hog-nose  drill  which  has  one  cutting  lip  only.  It  is 
carefully  ground  on  the  outside,  and  is  supplied  with  an  oil- 
duct  through  which  oil  at  high  pressure  may  be  brought  directly 
to  the  cutting  edge. 

Referring  to  Fig.  9,  A  is  the  cutting  edge,  B  the  oil-duct,  and 
C  the  chip  groove.  In  milling  the  latter  groove,  the  cutter  is 
brought  directly  to  the  center  line,  so  that,  in  this  respect, 


TEAT  F. 


>^ 


V.  y?,ty>/y///Vk  — 


Machinery 


Fig.  9.     Type  of  Deep-hole  Drill  adapted  to  Drilling  Rifle  Barrels 

the  drill  is  very  free  cutting  as  compared  with  the  ordinary 
two-lip  twist  drill  which  has  a  central  web.  In  the  end  view, 
the  shape  of  the  chip  groove  is  clearly  indicated.  The  cutting 
edge  A  is  radial.  In  sharpening  the  drill,  the  high  point  or 
part  first  entering  the  work  is  not  ground  in  the  center  as  is 
usually  the  case  in  drills,  but  to  one  side  as  shown  by  the  cross- 
section  D  of  the  work  being  drilled,  E  being  the  high  point  of 
the  drill.  Grinding  the  drill  in  this  manner  makes  possible  its 
running  true  or  straight,  the  teat  F  on  the  work  acting  as  a 
support  to  the  drill,  which,  owing  to  its  periphery  being  partly 


DEEP-HOLE  DRILLING  215 

relieved,  would  have  a  tendency  to  travel  in  a  curve  away  from 
its  cutting  side.  The  piece  being  drilled  is  run  at  very  high 
speed,  the  periphery  speed  at  the  outer  diameter  of  the  hole 
being  as  high  as  130  feet  per  minute  on  machine  steel.  The 
feed,  however,  is  quite  fine,  on  a  o.3-inch  drill  averaging  0.0004 
inch  per  revolution,  while  on  a  3-inch  drill  it  is  about  0.0008 
inch.  These  figures,  of  course,  are  dependent  to  a  great  extent 
upon  the  material  being  drilled.  The  drills  are  made  of  high- 
grade  steel  and  left  very  hard,  so  that  the  fine  feed  has  little 
tendency  to  glaze  the  cutting  edge. 

The  piece  being  drilled  is  held  and  revolved  at  one  end  by  a 
suitable  chuck  on  the  live  spindle  of  the  machine,  while  the 
other  end,  which  should  be  turned  perfectly  true,  runs  in  a 
stationary  bushing  having  at  its  outer  end  a  hole  the  diameter 
of  the  drill.  The  drill  enters  the  work  through  the  bushing, 
and  is  thus  started  perfectly  true.  The  arrangement  is  in- 
dicated in  the  middle  view,  in  which  G  represents  the  chuck,  H 
the  work,  /  the  bushing,  K  the  support  for  holding  the  bushing, 
and  L  the  drill.  Through  the  oil-duct  of  the  drill,  oil  is  forced 
at  a  pressure  varying  from  150  to  200  pounds  per  square  inch. 
After  passing  the  cutting  edge,  the  oil  returns  to  the  reservoir 
by  the  way  of  the  chip  groove,  forcing  the  chips  along  in  its 
travel.  In  drills  of  large  diameter,  especially  when  working 
on  tough,  stringy  material,  the  cutting  edge  is  usually  ground  so 
as  to  produce  a  number  of  shavings  instead  of  one  the  full  width 
of  the  cutting  lip,  so  that  no  trouble  is  experienced  in  getting 
chips  out  of  the  way.  The  oil,  of  course,  is  used  over  and  over 
again,  and  with  a  large  reservoir  will  be  kept  quite  cool. 

The  drill  is  made  up  of  the  drill  tip  and  shank,  the  tip  varying 
in  length  from  4  to  8  inches,  while  the  length  of  the  shank  is 
determined  by  the  depth  of  hole  that  is  to  be  drilled.  The 
shanks  on  small  drills  are  made  from  steel  tubing,  rolled  to 
special  cross-sectional  form.  The  tip  is  carefully  fitted  and 
soldered  to  the  shank,  which,  it  should  be  noted,  is  a  little 
smaller  in  diameter  than  the  tip. 

The  relief  or  clearance  of  the  cutting  edge  of  the  drill,  the 
amount  the  "  high  point  "  of  the  drill  should  be  off  center, 


I4  G 


2l6 


MODERN  DRILLING  PRACTICE 


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DEEP-HOLE  DRILLING  217 

is  about  |  inch  on  a  one-inch  drill.  The  surface  x  is  left  of 
the  full  radius  of  the  drill,  and  makes  a  good  back-rest.  When 
the  drill  is  ground  on  its  periphery,  it  is  made  very  slightly 
tapering  toward  the  shank  in  order  to  free  itself.  As  previ- 
ously stated,  in  milling  the  chip  groove,  the  cutter  is  brought 
exactly  to  the  center  of  the  drill.  When  hardening  and  grind- 
ing, however,  the  location  frequently  changes  slightly  so  that 
the  groove  does  not  come  to  the  center  of  the  drill.  In  such 
cases,  it  is  necessary  to  grind  out  the  lip  at  the  point. 

Rifle  Barrel  Drilling  Machine.  —  The  rifle  barrel  drilling 
machine  illustrated  in  Fig.  10  (made  by  the  Diamond  Machine 
Co.)  operates  on  the  general  principle  previously  referred  to, 
the  work  being  revolved  while  the  drill  remains  stationary, 
except  for  the  slow  feeding  movement.  Any  machinist  who 
has  had  experience  in  the  drilling  of  deep  holes  will  appreciate 
the  difficulties  encountered  in  drilling  a  hole  through  steel  rifle 
barrels  30  inches  in  length  and  maintaining  an  extremely  high 
degree  of  accuracy  in  the  work.  The  most  noteworthy  feature 
of  the  operation  to  the  mechanic  who  has  had  experience  in 
drilling  deep  holes  with  ordinary  drills,  where  it  is  necessary 
to  back  the  drill  out  at  frequent  intervals  in  order  to  clear 
the  chips,  is  the  fact  that  the  operation  is  continuous  when 
the  proper  equipment  is  used.  This  has  been  made  possible, 
in  part,  by  using  special  drills  of  the  general  type  previously 
referred  to.  As  these  drills  are  made  hollow,  a  copious  flow  of 
cutting  compound  may  be  delivered  right  to  the  point  of  the 
drill  where  it  is  most  effective  in  dissipating  the  heat  of  the  cut. 
The  oil  escapes  through  the  flute  extending  along  one  side  of 
the  drill  which  also  provides  means  of  washing  away  the  chips 
as  fast  as  they  are  produced. 

The  drill  is  made  of  sufficient  length  to  extend  entirely 
through  the  rifle  barrel.  The  body  of  the  drill  is  made  of  steel 
tubing  which  is  rolled  in  at  one  side  in  order  to  produce  the 
groove  which  provides  for  the  escape  of  oil  and  chips  from  the 
work.  The  point  of  the  drill  is  made  of  drill  rod.  A  groove  is 
ground  down  the  side  of  the  drill  in  order,  to  continue  the  groove 
which  has  been  rolled  in  the  steel  tube,  and  the  drill  point  is 


2l8  MODERN  DRILLING  PRACTICE 

soldered  to  the  end  of  the  tube.  The  description  will  be  better 
understood  by  referring  to  Fig.  n  which  shows  one  of  the  drills. 
The  drilling  machine  provides  for  working  on  two  rifle  barrels 
at  a  time.  The  barrel  forging  is  supported  in  a  chuck  in  the 
headstock  spindle,  this  chuck  consisting  of  a  tapered  socket 
which  is  serrated  so  that  a  firm  grip  is  secured  on  the  work 
when  the  end  of  the  forging  is  driven  into  place  by  tapping  the 
opposite  end  of  the  barrel  with  a  lead  hammer.  The  outer  end 
of  the  work  is  supported  by  a  bushing  at  the  left-hand  side  of 
rest  A,  Fig.  10,  and  at  the  right-hand  side  of  this  rest  there  is  a 
guide  bushing  which  is  a  close  fit  around  the  point  of  the  drill.  As 


Fig.  ii.     Cutting  End  of  a  Rifle  Barrel  Drill 

the  work  rotates,  the  drill  is  fed  to  the  work  by  traversing  the 
tails tock  in  which  the  shank  of  the  drill  is  supported.  As  the 
drills  are  long  and  thin,  it  will  be  evident  that  some  intermediate 
support  is  necessary,  and  this  support  is  afforded  by  means  of 
a  steadyrest.  This  description  and  that  which  follows  apply 
to  one  side  of  the  machine,  but  it  will  be  evident  that  the  entire 
machine  is  composed  of  two  sets  of  mechanism  like  that  de- 
scribed. 

Driving  Mechanism  of  Rifle  Barrel  Drilling  Machine.  —  The 
arrangement  of  the  drive  will  be  best  understood  by  referring 
to  Fig.  12  which  shows  the  mechanism  quite  clearly,  but  in 
connection  with  this  description  it  should  be  understood  that 
guards  are  provided  over  all  gearing  on  the  machine.  The 
drill  at  the  front  of  the  machine  is  driven  by  pulley  A  which  is 
mounted  at  the  back  of  the  spindle,  and  the  power  is  transmitted 
through  a  friction  clutch  B  which  is  held  in  engagement  by  the 
pointed  end  of  lever  C  that  engages  a  shoulder  at  the  end  of  the 


DEEP-HOLE  DRILLING 


2I9 


horizontal  rod  D.  When  the  tails  took  has  been  traversed  far 
enough  along  the  bed  of  the  machine  so  that  the  hole  has  been 
drilled  entirely  through  the  rifle  barrel,  a  dog  on  the  tailstock 
engages  an  adjustable  stop  carried  by  rod  D,  with  the  result 
that  this  rod  is  rocked  down  so  that  the  shoulder  disengages 
the  end  of  lever  C.  As  a  result,  compression  spring  E  becomes 
effective  and  throws  clutch  B  out  of  engagement,  thus  stopping 


Fig.  12.    Close  View  of  Driving  Mechanism  with  Gear  Guard  removed 

both  the  rotation  of  the  spindle  and  the  feeding  of  the  drill  to 
the  work.  The  feed  motion  for  the  tailstock  is  transmitted 
from  the  spindle  through  a  worm  and  wheel,  change-gears  F, 
and  a  second  worm  and  wheel  to  a  lead-screw  located  inside  the 
bed  of  the  machine.  This  lead-screw  traverses  the  tailstock 
in  the  same  way  that  the  lead-screw  of  an  ordinary  engine 
lathe  moves  the  carriage  along  the  bed  of  the  machine. 

Oil  Supply  for  Rifle  Barrel  Drilling  Machine.  —  In  connec- 
tion with  the  description  of  the  drill  it  was  mentioned  that 
means  are  provided  for  clearing  the  chips  from  the  hole  by  de- 
livering a  flow  of  oil  through  a  tube  in  the  drill  and  allowing  it 
to  escape  by  way  of  a  groove  at  the  side.  The  oil  employed 


220 


MODERN  DRILLING  PRACTICE 


for  this  purpose  is  contained  in  a  reservoir  located  beneath 
the  machine,  and  the  pump  which  is  connected  with  this  reser- 
voir is  shown  at  G,  this  pump  being  driven  by  a  large  pulley  at 
the  left-hand  end  of  the  machine.  In  order  to  provide  for 
supplying  the  hollow  drill  with  oil  as  the  tailstock  is  traversed 
along  the  bed  of  the  machine,  connection  is  made  with  the 
tailstock  and  end  of  the  hollow  drill  by  means  of  a  telescopic 
tube  H  through  which  oil  is  pumped  from  the  reservoir.  In 


Fig.  13.     End  View  of  Machine,  showing  Tailstock  Buffer  Springs 

order  to  secure  satisfactory  results  in  clearing  the  chips  from 
the  hole,  it  is  necessary  to  have  the  oil  at  a  pressure  of  not 
less  than  800  pounds  per  square  inch,  and  under  actual  work- 
ing conditions  this  pressure  is  generally  quite  close  to  1000  pounds 
per  square  inch.  This  pressure  resists  the  action  of  the  lead- 
screw  in  traversing  the  tailstock  along  the  bed,  and  results  in  a 
tendency  for  the  tailstock  to  move  over  toward  the  right-hand 
end  of  the  bed. 

After  the  drilling  operation  has  been  completed,  the  split 
nut  by  which  connection  is  made  between  the  lead-screw  and 
tailstock  is  released  in  order  to  move  the  tailstock  back  to  the 


DEEP-HOLE  DRILLING  221 

starting  position.  Evidently  when  the  split  nut  is  released  in 
this  way  there  is  a  possibility  of  the  residual  pressure  in  the 
oil-tube  causing  the  tailstock  to  be  thrown  back  with  consider- 
able force,  and  cases  are  on  record  where  a  machine  has  actually 
been  wrecked  in  this  way.  To  obviate  trouble  from  this 
source,  a  buffer  spring  is  provided  as  shown  at  A,  Fig.  13,  which 
will  absorb  the  shock  in  case  the  tailstock  is  thrown  back  in 
this  way.  It  will  be  evident  that,  with  oil  at  a  pressure  ex- 
ceeding 800  pounds  per  square  inch,  it  is  necessary  to  provide 
an  effective  form  of  guard  to  prevent  it  from  being  thrown  from 
the  point  at  which  it  escapes  from  the  end  of  the  hole  in  the 
work.  These  means  are  provided  by  guard  A,  Fig.  10,  which 
carries  the  bushing  that  supports  the  outer  end  of  the  rifle 
barrel ;  the  oil  and  chips  escape  into  this  guard  from  which  they 
drop  down  into  the  pan  under  the  machine.  This  pan  is  pro- 
vided with  a  strainer  which  holds  back  the  chips,  but  allows 
the  oil  to  flow  through  into  the  reservoir  where  it  is  ready  to 
once  more  be  pumped  to  the  work. 

When  working  on  military  rifles,  these  machines  are  ordi- 
narily driven  at  a  speed  of  1500  revolutions  per  minute,  and 
the  drill  is  fed  to  the  work  at  rates  of  feed  which  cover  a  range 
of  from  0.2  to  i.o  inch  per  minute.  The  rate  of  production  is 
about  three  barrels  per  hour  from  each  two-spindle  machine, 
i.e.,  a  barrel  forging  can  be  set  up  in  the  machine,  and  drilled 
and  removed  in  approximately  forty  minutes. 

Twelve-spindle  Rifle  Barrel  Drilling  Machine.  —  A  radical 
departure  from  the  conventional  method  of  drilling  and  ream- 
ing rifle  barrels  has  been  made  in  the  machines  shown  in  Figs.  14 
and  15,  designed  by  the  New  England  Westinghouse  Co.  These 
machines  differ  from  standard  rifle  barrel  drilling  and  reaming 
machines  in  several  important  respects:  First,  they  are  de- 
signed to  handle  the  barrels  vertically  instead  of  horizontally; 
second,  twelve  instead  of  two  barrels  are  handled  by  each  ma- 
chine; third,  each  spindle  on  the  barrel  drilling  machine  is 
driven  by  a  separate  variable-speed  motor;  fourth,  one  machine 
occupies  exactly  the  same  floor  space  as  the  standard  machine, 
which  has  a  capacity  for  only  two  instead  of  twelve  barrels; 


222 


MODERN   DRILLING  PRACTICE 


fifth,  on  the  drilling  machine  an  automatic  electric  switch  in- 
stead of  a  mechanically-operated  clutch  is  provided  for  stopping 
the  machine  should  a  drill  stick  or  become  dull;  and  sixth,  on 
the  barrel  reaming  machine,  the  feed  is  by  counterweights 
instead  of  a  positive  screw,  thus  automatically  adjusting  the 


Fig.  14.     Westinghouse  Rifle  Barrel  Drilling  Machine  that  Works 
on  Twelve  Barrels  simultaneously 

rate  of  feed  to  suit  varying  conditions  in  the  size  of  bore  and 
hardness  of  metal. 

The  machine  consists  of  an  upright  frame  standing  on  a  base 
of  rectangular  section  and  carrying  twelve  individual  units, 
comprising  a  variable-speed  motor,  headstock,  tailstock,  drill 
guide,  carriage,  and  controller,  the  controller  being  located  at 
the  rear  of  the  machine.  All  these  members,  with  the  exception 
of  the  motor  and  headstock,  are  carried  on  twelve  uprights. 


DEEP-HOLE   DRILLING 


223 


111 


Fig.  15. 


Westlnghouse  Twelve-spindle  Rifle  Barrel 
Reaming  Machine 


In  operation,  the  rifle  barrel  to  be  drilled  is  held  in  and 
rotated  by  the  headstock,  a  female  driving  chuck  or  center 
with  sharp  projections  contacting  with  the  machined  taper  on 
the  muzzle  end  of  the  barrel.  This  chuck  is  connected  directly 
to  the  motor  shaft.  The  lower  center  in  the  tailstock  is  held 
upward  by  a  stiff  spring,  thus  insuring  that  the  barrel  is  always 
held  up  in  the  chuck  with  the  same  pressure,  and  at  the  same 


224  MODERN  DRILLING  PRACTICE 

time  providing  for  linear  expansion  of  the  barrel  due  to  heat- 
ing while  it  is  being  drilled.  The  carriage  is  furnished  with 
the  standard  type  of  oil-tube  barrel  drill  and  is  fed  upward  by  a 
lead-screw  that  receives  power  from  the  motor  through  a  train 
of  gears,  worms,  and  worm-wheels. 

The  oil  is  pumped  up  through  the  drill  from  an  oil  "  line  " 
in  which  the  pressure  registers  about  800  pounds  per  square 
inch.  The  oil  and  chips  pass  down  through  the  exterior  flute 
in  the  drill  and  shank,  and  are  carried  off  through  a  "  by-pass  " 
pipe  which  is  part  of  the  tailstock  casting.  This  pipe  extends 
to  the  rear  of  the  machine  and  empties  into  a  trough  in  which 
the  chips  are  separated  from  the  oil,  which  returns  to  the  pump. 

Each  spindle  is  automatically  stopped  when  the  drill  breaks 
through  at  the  muzzle  end  of  the  barrel  by  a  dog  which  operates 
the  starting  and  stopping  handle.  An  interesting  feature  in 
connection  with  this  machine,  which  eliminates  the  splashing 
of  oil  when  the  drill  breaks  through,  is  a  "  by-pass  "  arrange- 
ment consisting  of  angular  holes  in. the  lower  section  of  the 
headstock  casting.  This  "  by-pass  "  conveys  oil  from  the  drill 
to  a  pipe  which,  in  turn,  carries  it  to  a  trough  behind  the  ma- 
chine. In  this  way,  the  machine  is  kept  clean  and  free  from  oil. 

Another  feature,  which  relates  more  particularly  to  the  elec- 
trical equipment,  is  the  provision  made  for  stopping  the  ma- 
chine automatically,  should  the  drill  become  dull  or  stick  and 
thus  consume  more  power  than  would  ordinarily  be  required. 
This  consists  of  an  electric  switch,  comprising  an  overload  coil 
which  is  connected  in  series  with  the  armature,  and  is  so  ar- 
ranged that  any  excess  current  passing  through  the  armature 
will  operate  the  coil  and  through  it  the  switch,  thus  automati- 
cally stopping  the  machine.  This  overload  coil  can  be  very 
accurately  adjusted  to  suit  conditions  of  steel,  etc.  A  starting 
rheostat  is  also  provided  which  enables  work  speeds  varying 
from  1 200  to  2400  revolutions  per  minute  to  be  obtained. 

Rifle  Barrel  Reaming  Machine. —  In  the  rifle  barrel  ream- 
ing machine  shown  in  Fig.  15,  advantage  is  taken  of  the  vertical 
principle  of  handling  the  work.  Reaming  on  vertical  machines 
comprises  several  important  advantages  over  the  horizontal 


DEEP-HOLE  DRILLING  225 

method.  In  the  first  place,  twelve  spindles  occupy  exactly 
the  same  floor  space  as  two  spindles  of  a  horizontal  machine r 
and  present  the  spindles  in  compact  form,  so  that  they  can  be 
attended  to  by  one  operator.  In  the  second  place,  lubrication 
of  the  reamer  is  more  easily  accomplished,  resulting  in  the  pro- 
duction of  holes  free  from  rings  and  other  defects. 

There  are  several  other  advantages  incorporated  in  this  ma- 
chine, among  which  are  the  following:  First,  the  barrels  are 
swung  from  universal  joints,  enabling  the  reamers  to  follow 
the  drilled  holes  accurately.  Second,  the  feed  is  by  counter- 
weights —  not  positive  —  so  that  it  automatically  adjusts  itself 
to  agree  with  the  amount  of  work  being  done  by  the  reamers. 
For  instance,  if  there  is  more  material  to  be  reamed  out  of  a 
hole  than  is  normally  the  case,  the  machine  will  feed  more 
slowly;  and  if  the  reamer  strikes  a  hard  spot  in  the  barrel^ 
the  feed  will  slow  up  to  accomodate  itself  to  this  condition. 
Third,  the  machine  can  be  used  either  for  push  or  pull  ream- 
ing. This  is  accomplished  by  changing  the  direction  of  driv- 
ing rotation  of  the  belt  on  the  cone  pulley  at  the  left-hand  end 
of  the  machine,  and  by  changing  the  location  of  the  counter- 
weights. 

The  feed  for  t'he  reamers,  as  previously  mentioned,  is  ob- 
tained by  means  of  counterweights  which  are  placed  on  cross- 
heads  or  at  opposite  ends  of  the  cables,  depending  upon  whether 
the  push  or  pull  method  is  being  used.  These  cables  run  over 
pulleys  that  are  mounted  on  friction  clutches  so  arranged  that 
they  can  be  made  to  work  in  either  direction.  The  weights 
can  also  be  adjusted  to  give  any  rate  of  feed  that  is  found  most 
satisfactory  for  the  steel  being  machined  and  the  amount  of 
material  being  removed.  All  twelve  spindles  are  driven  from 
one  longitudinal  shaft  running  the  entire  length  of  the  machine, 
which,  in  turn,  is  operated  from  a  countershaft  located  on  the 
floor. 


INDEX 


Air  hose  for  blowing  away  chips,  161 
Almond,  J.  R.,  Mfg.,  Co.'s  geared 
type  of  chuck,  122 

American  Tool  Works  Co.'s  radial  drill- 
ing machine,  20 

Angles,  of  drill  points,  126 

rake  and  spiral,  of  twist  drills,  106 

Assembling  machine  parts  with  drilling 
machine,  171 

Automatic   compressed-air  reverse  for 
threading  and  tapping,  158 

Automatic  drill  chucks,  118 

Automatic  drilling  machines,  4 

Automatic  speed  adjustment,  for  drill- 
ing machines,  89 

Auxiliary  multiple  drilling  heads  and 
drill  speeders,  57 

Baker   Bros.'   high-duty   drilling   ma- 
chines, 13,  14,  18 

Baker    Bros.'    semi-automatic    drilling 
machines,  67 

Ball-bearing  sensitive  drilling  machine, 

ii 
high-speed,  7 

Barnes  Drill  Co.'s  drilling  machine  for 
high-explosive  shells,  206 

Baush  Machine  Tool    Co.'s    multiple- 
spindle  drilling  machines,  40,  42 

Baush   Machine    Tool    Co.'s    station- 
type  drilling  machines,  47,  54 

Bowser  &  Co.,  S.  F.,  drilling  practice, 
142,  191 

Broaching    operation    on    drilling   ma- 
chine, 167 

Cannon  drills,  1 06 

Caulkins    and    Carpenter    drilling 

jig,  8 
Celfor  Tool  Co.'s  drill  chuck,  124 


Center  drill  and  countersink,  105 
Chips  removed  by  means  of  air  hose,  161 
Chucks,  collet,  quick-change,  115 
drill,  automatic,  118 
drill,  for  special  drill  shanks,  123 
drill,  two-jaw  screw-  type,  120 
drill,  types  commonly  used,  1  14 
drill,  wrenchless  type,  122 
geared-  type,  121 
Cincinnati-Bickford  radial  drilling  ma- 

chine, 22 
Cincinnati  Machine  Tool  Co.'s  revers- 

ing drilling  machine,  168 
Cincinnati    Pulley    Co.'s    ball-bearing 

sensitive  drilling  machine,  1  1 
Clamping  devices  for  jigs,  181 
Clearance  behind  cutting  edges,  127 
Cluster-type    multiple-spindle    drilling 

machines,  36 
Colburn    Machine   Tool    Co.'s   heavy- 

duty  drilling  machines,  32 
Collet  chucks,  quick-change,  115 
Compressed  air  for  ejecting  work  from 

fixtures,  35 
Compressed-air  reverse,  automatic,  for 

threading  and  tapping,  158 
Continuous-feed  drilling  machine,  six- 

head,  73 
Coolants  and  lubricants  used  for  drill- 

ing, 101 

Cotter-pin  hole  drilling  machine,  71 
Countersink  and  center  drill,  105 
Critical  drilling  speeds,  90 
Cushman    Chuck    Co.'s    two-jaw   drill 

chuck,  1  20 
Cutters,  facing,  special  form,  188 


equivalents  of  nominal  sizes 
of  drills,  table,  88 
Deep-hole  drill,  213 


226 


INDEX 


227 


Deep-hole  drilling,  202 

why  work  is  revolved,  212 
Deep-hole  drilling  machines,  horizontal, 
209 

vertical,  208 

Deep-hole  work,  inverted  drilling,  203 
Detroit   Tool   Co.'s   five-spindle   semi- 
automatic drilling  machine,  63 
Detroit  Twist  Drill  Co.'s  drill  chuck, 

124 
Diamond    Machine    Co.'s    rifle    barrel 

drilling  machine,  217 
Drill  chucks,  automatic,  118 

for  special  drill  shanks,  123 

two-jaw  screw- type,  120 

types  commonly  used,  114 

wrenchless,  122 
Drill  grinding,  125 

effect  of  improper,  136 
Drill  grinding  machines,  use  of,  133 
Drill  heads,  multiple,  and  drill  speeders, 

57 

multiple-spindle,  for  vertical  drilling 

machines,  34 
Drilling,  at  high  speed,  advantages,  82 

deep-hole,  202 

inverted,  for  deep-hole  work,  203 

reaming,  and  counterboring  on  mul- 
tiple-spindle machines,  45 
Drilling  machines,   applied   to  general 
manufacturing  operations,  142 

arrangement,  143 

assembling  parts  on,  171 

automatic,  4 

automatically  controlled,  63 

equipped  for  milling  operations,  166 

five-spindle,  with  indexing  fixture,  55 

general  types,  2 

high-duty  vertical,  3 

high-speed  ball-bearing  sensitive,  7 

horizontal  deep-hole,  209 

multiple  indexing,  61 

multiple-spindle,  4,  28 

multiple-spindle  cluster  type,  36 

multiple-spindle,  special,  43 

multiple-spindle  station-type,  47 

multiple-spindle    straight-line    type, 
29 


Drilling  machines,  multiple-spindle, 
used  for  drilling,  reaming,  and 
counterboring,  45 

number  used  progressively,  143 

order  of  operations,  145 

portable  pneumatic,  175 

power  required  for  driving,  100 

radial,  3,  20 

range  of  work,  142 

rifle  barrel,  217 

rifle  barrel,  oil  supply,  219 

rifle  barrel,  twelve-spindle,  221 

semi-automatic  five-spindle,  63 

semi-automatic  sensitive,  9 

semi-automatic  six-spindle,  66 

semi-automatic  twelve-spindle,  76 

sensitive,  arranged  to  automatically 
control  spindle  movements,  1 1 

special  equipment,  155 

special  threading  and  tapping  mecha- 
nism, 156 

station-type,  equipped  with  inverted 
drills,  54 

turret- type,  5,  24 

vertical  deep-hole,  208 

vertical  high-duty,  13 

vertical  or  upright,  2 

vertical  or  upright,  operation,  6 
Drilling  speeds  and  feeds,  82 
Drilling  speeds,  critical,  90 
Drill  points,  angles,  126 
Drills,  cannon,  106 

causes  of  broken,  137 

flat,  104 

for  deep  holes,  213 

four-fluted,  104 

gagingor measuring  after  grinding,  132 

high-speed  steel,  effect  of  high  speeds, 
96 

hollow  and  rifle  barrel,  105 

inverted,    for    use    on    station- type 
drilling  machines,  54 

method  of  grinding  by  hand,  133 

nominal  sizes,  decimal    equivalents, 
table,  88 

oil  tube,  105 

sizes    of,    used    with    Morse    taper 
shanks,  table,  no 


228 


INDEX 


Drills,  speeds  and  feeds  for  high-speed 

and  carbon  steel,  tables,  93 
straight-fluted,  104 
teat,  104 
three-fluted,  104 

twist,  rake  and  spiral  angles,  106 
twist,  two-fluted,  102 
types  of,  102 

with  broken  tangs,  methods  of  utiliz- 
ing, 112 

Drill  shanks,  107 
Drill  sockets,  no 

Drill  speeders  and  auxiliary  multiple 
drilling  heads,  57 

Eclipse  Interchangeable  Counterbore 
Co.'s  "Wiard"  chuck,  117 

Electrical  connections  for  portable  tools, 
161 

Equipment,  special,  for  drilling  ma- 
chines, 155 

Errington  stud  setter,  169 

Facing  cutters,  special  form,  188 

Facing  operations,  disengagement 

of  feed,  162 
Feed,  accuracy  in  tripping,  185 

for  facing  operations,  disengagement, 

162 

Feed  pressure  and  torsion,  determina- 
tion of  magnitude,  139 
Feed  pressure  required  for  drilling,  97 
Feed  range,  fixture  for  increasing,  64 
Feeds  and  speeds,  for  drilling,  82 

for  high-speed  and  carbon  steel  drills, 

tables,  93 
recommended,  83 
Five-spindle  drilling  machine,  with  in- 

'  dexing  fixture,  55 
Five-spindle     semi-automatic     drilling 

machines,  63 

Fixtures  and  jigs,  materials  used,  182 
special  features,  189 
types,  183 
Fixtures,  indexing,  on  multiple-spindle 

machines,  38 

jigs  and  special  tools  for  drilling  ma- 
chines, 177 


Fixtures,  sliding,  applied  to  multiple- 
spindle  machine,  42 
tools,  and  jigs,  special  designs,  184 
work-holding,     for    increasing    feed 

range,  64 
Flat  drills,  104 

Foote-Burt  Co.'s  multiple-spindle  drill- 
ing machines,  29,  43 
Forming  operation  on  drilling  machine, 

175 

Four-fluted  drills,  104 
Four-spindle  drilling  head,  59 

gaging  or  measuring  drills  after  grind- 
ing, 132 

Geared-type  chuck,  121 
Goodell  Pratt  Co.'s  drill  chuck,  123 
Graham  grooved  shank,  123 
Grinding,  drill,  125 
Grinding  machines,  drill,  use  of,  133 
Gronkvist  automatic  drill  chuck,  119 

High-duty  drilling  machine,   vertical, 

3,  i3 

High-speed  drilling,  advantages,  82 
High-speed  steel  drills,  effect  of  high 

speeds,  96 

Hollow  and  rifle  barrel  drills,  105 
Horizontal  deep-hole  drilling  machine, 

209 
Horton,  E.,  &  Son  Co.'s  knurled-sleeve 

chuck,  123 

Indexing  fixture,  for  inverted  tools,  206 

for  machine  of  cluster  type,  38 
for  semi-automatic  drilling  machines, 

67 

for  use  on  five-spindle  drilling  ma- 
chines, 55 

Indexing  multiple  drilling  machine,  61 
Ingersoll-Rand    Co.'s    portable    pneu- 
matic drilling  machine,  175 
Inverted  drilling  for  deep-hole  work,  203 
Inverted  drills  for  use  on  station-type 

drilling  machines,  54 
Inverted  tools  held  on  indexing  fixture, 
206 


INDEX 


229 


Jacob  Mfg.  Co.'s  geared  type  of  chuck, 

121 

Jig  design,  essential  features,  178 
Jigs  and  fixtures,  materials  used,  182 
special  features,  189 
types,  183 

Jigs,  drilling,  Caulkins  and  Carpenter,  8 
fixtures,  and  special  tools  for  drilling 

machines,  177 
sliding,  for  multiple-spindle  drilling 

machines,  32 
tools,  and  fixtures,  special   designs, 

184 

traveling,  used  in  conjunction  with 
machines  of  cluster  type,  40 

J_,angelier  Mfg.  Co.'s  drilling  machines, 
motor  valve  sleeve  multiple- 
type,  80 

multiple-head,  61 
multiple-spindle,  45 
semi-automatic  continuous-feed,  71 
semi-automatic  twelve-spindle,  76 
six-head  continuous-feed,  73 
Leland-Gifford  drilling  machines,  semi- 

automatic sensitive-type,  9 
sensitive  ball-bearing,  7 
Locating  points,  for  jigs,  180 
Lubricants  and  coolants  used  for  drill- 
ing, 101 


tion  performed  on  drilling 
machine,  166 

Modern  Tool  Co.'s  "  Magic"  chuck,  115 
Multiple  drilling  heads  and  drill  speed- 

ers, 57 

Multiple  drilling  machine,  indexing,  61 
Multiple-spindle  drill  heads,  for  verti- 

cal drilling  machines,  34 
Multiple-spindle  drilling  machines,  4,  28 
cluster  type,  36 
sliding  jigs,  32 
special  type,  43 
station-type,  47 
straight-line  type,  29 
used  for  drilling,  reaming,  and  coun- 

terboring,  45 
with  indexing  fixture,  55 


Acme  Co.'s  six-spindle  semi- 
automatic drilling  machine,  66 

National  Automatic  Tool  Co.'s  mul- 
tiple-spindle drilling  machine,  38 

National  Twist  Drill  and  Tool  Co.'s 
"Graham"  grooved  shank  drill, 
123 

Newman  Mfg.  Co.'s  turret-type  drilling 
machine,  26 

Nielsen-Barton  Chuck  Co.'s  drill  chuck, 
123 

Oil  tube  drills,  105 

Organization  of  drilling  department 
management,  146 

Pneumatic  drilling  machine,  portable, 

175 

Portable  tools,  electrical  connections, 
161 

Power  required  to  drive  drilling  ma- 
chines, 100 

Pratt  Chuck  Co.'s  chuck,  120 

Pressure  required  for  drilling,  97 

Production  rates,  200 

Quick-action  Chuck  Co.'s  drill  chuck, 

117 

Quick-change  collect  chucks,  115 
Quint  turret-type  drilling  machine,  24 

Radial  drilling  machines,  3,  20 

Rake  and  spiral  angles    of    twist 

drills,  106 

Rates  of  production,  200 
Reaming  machine,  rifle  barrel,  224 
Rich  Tool  Co.'s  drill  chuck,  124 
Rifle  barrel  and  hollow  drills,  105 
Rifle  barrel  drilling  machines,  217 
oil  supply,  219 
twelve-spindle,  221 
Rifle  barrel  reaming  machine,  224 
Rockford  Drilling  Machine  Co.'s  drill- 
ing machines,  for  assembling  uni- 
versal joints,  173 
four-spindle  gang,  203 
high-duty,  166 
vertical,  6,  34 


230 


INDEX 


Screw-type  two-jaw  drill  chucks,  120 
Sellew  Machine  Tool  Co.'s  four- 
spindle  drilling  head,  59 
Semi-automatic  drilling  machines,  five- 
spindle,  63 
sensitive,  9 
six-spindle,  66 
twelve-spindle,  76 
with  indexing  fixture,  67 
Sensitive  drilling  machines,  arranged  to 
automatically  control  spindle  move- 
ments, ii 

high-speed  ball-bearing,  7 
semi-automatic,  9 
Shanks,  drill,  107 

Six-head   continuous-feed  drilling  ma- 
chine, 73 

Six-spindle  semi-automatic  drilling  ma- 
chine, 66 
Skinner  Chuck  Co.'s  geared-type  chuck, 

122 
Sliding  fixture  applied  to  machine  of 

cluster  type,  42 

Sliding  jigs  for  multiple-spindle  opera- 
tion, 32 

Sockets,  drill,  no 

Speed  adjustment,  automatic,  for  drill- 
ing machine,  89 

Speeds  and  feeds,  for  drilling,  82 
for  high-speed  and  carbon  steel  drills, 

tables,  93 
recommended,  83 
Speeds,  drilling,  critical,  90 

in  R.P.M.  for  given  cutting  speed, 

86,87 

of  modern  drilling  machines,  95 
Spiral  and  rake  angles  of  twist  drills, 

106 
Station-type  drilling  machine  equipped 

with  inverted  drills,  54 
Station-type    multiple-spindle    drilling 

machines,  47 

Stecher,   Charles,   Co.'s  vertical  deep- 
hole  drilling  machine,  208 
Straight-fluted  drills,  104 
Straight-line    multiple-spindle    drilling 

machines,  29 
Studs  driven  by  power,  169 


Tangs  on  drills,  methods  of  using  when, 
broken,  112 

Tapping  and  threading  operations,  spe- 
cial mechanism  for,  156 

Tapping  and  threading  with  automatic 
compressed-air  reverse,  158 

Teat  drills,  104 

Threading  and  tapping  operations,  spe- 
cial mechanism  for,  156 

Threading  and  tapping  with  automatic 
compressed-air  reverse,  158 

Three-fluted  drills,  104 

Tools,  portable,  electrical  connections, 
161 

Torsion  and  feed  pressure,  determina- 
tion of  magnitude,  139 

Traveling  jigs  used  in  conjunction  with 
machines  of  cluster  type,  40 

Tripping  feed  accurately  at  a  given 
point,  185 

Turner  Machine  Co.'s  turret- type  drill- 
ing machines,  26 

Turret-type  drilling  machines,  5,  24 

Twelve-spindle  rifle  barrel  drilling  ma- 
chine, 221 

Twelve-spindle  semi-automatic  drilling 
machine,  76 

Twist  drills,  rake  and  spiral  angles,  106 
two-fluted,  102 

Two-jaw  screw-type  drill  chucks,  120 

Under-cutting  tool,  design  of,  187 
Upright  or  vertical  drilling  machines,  2 
operation,  6 

\falve  sleeve  multiple  drilling  machine, 

80 

Vertical  deep-hole  drilling  machine,  208 
Vertical  or  upright  drilling  machines,  2 
operation,  6 

\Vahlstrom  Tool  Co.'s  eccentric  chuck, 
118 

Washburn  four-spindle  drilling  ma- 
chines, 30 

Westcott  Chuck  Co.'s  chuck,  120 

Whitney  Mfg.  Co.'s  "Presto"  chuck, 
116 

Wrenchless  drill  chucks,  122 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN     INITIAL     FINE     OF     25     CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


OCT  19  1932 


OCT 


1935 


OCT  ,20  1935 


EP   111938 


NOV    27  1938 
AP3  5    1939 


LD  21-50m-8,'32 


416064 

"7X 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


m 


